/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: main

Fyi, I started seeing this error today during buildworld compile.

FreeBSD BSD_12 12.0-CURRENT FreeBSD 12.0-CURRENT #15 r331021: Thu Mar 15 
16:30:40 EDT 2018 
root_at_BSD_12:/usr/obj/usr/src/amd64.amd64/sys/MYKERNEL  amd64 1200060

# svnlite info
Path: .
Working Copy Root Path: /usr/src
URL: svn://svn.freebsd.org/base/head
Relative URL: ^/head
Repository Root: svn://svn.freebsd.org/base
Repository UUID: ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Revision: 331135
Node Kind: directory
Schedule: normal
Last Changed Author: markj
Last Changed Rev: 331135
Last Changed Date: 2018-03-18 13:03:26 -0400 (Sun, 18 Mar 2018)
-------------------------------------------------------------------------------------

--- all_subdir_lib/libcasper ---
--- all_subdir_lib/libcasper/services/cap_sysctl ---
/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: main
>>> referenced by crt1.c:74 (/usr/src/lib/csu/amd64/crt1.c:74)
>>>               /usr/obj/usr/src/amd64.amd64/tmp/usr/lib/crt1.o:(_start)
/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_create
>>> referenced by cap_sysctl.c:64 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:64)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_add_string
>>> referenced by cap_sysctl.c:65 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:65)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_add_string
>>> referenced by cap_sysctl.c:66 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:66)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_add_number
>>> referenced by cap_sysctl.c:67 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:67)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_add_null
>>> referenced by cap_sysctl.c:69 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:69)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_add_number
>>> referenced by cap_sysctl.c:71 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:71)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_add_binary
>>> referenced by cap_sysctl.c:73 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:73)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
cap_xfer_nvlist
>>> referenced by cap_sysctl.c:74 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:74)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_get_number
>>> referenced by cap_sysctl.c:77 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:77)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_get_number
>>> referenced by cap_sysctl.c:78 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:78)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_destroy
>>> referenced by cap_sysctl.c:79 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:79)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_get_number
>>> referenced by cap_sysctl.c:84 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:84)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_get_binary
>>> referenced by cap_sysctl.c:86 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:86)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_destroy
>>> referenced by cap_sysctl.c:91 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:91)
>>>               /tmp/cap_sysctl-cfa2f8.o:(cap_sysctlbyname)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
service_register
>>> referenced by cap_sysctl.c:295 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:295)
>>>               /tmp/cap_sysctl-cfa2f8.o:(init_casper_service)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_next
>>> referenced by cap_sysctl.c:209 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:209)
>>>               /tmp/cap_sysctl-cfa2f8.o:(sysctl_limit)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_get_number
>>> referenced by cap_sysctl.c:212 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:212)
>>>               /tmp/cap_sysctl-cfa2f8.o:(sysctl_limit)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_next
>>> referenced by cap_sysctl.c:209 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:209)
>>>               /tmp/cap_sysctl-cfa2f8.o:(sysctl_limit)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: undefined symbol: 
nvlist_error
>>> referenced by cap_sysctl.c:110 
(/usr/src/lib/libcasper/services/cap_sysctl/cap_sysctl.c:110)
>>>               /tmp/cap_sysctl-cfa2f8.o:(sysctl_command)

/usr/obj/usr/src/amd64.amd64/tmp/usr/bin/ld: error: too many errors 
emitted, stopping now (use -error-limit=0 to see all errors)
--- all_subdir_lib/libpam ---
--- pam_setcred.3.gz ---
gzip -cn /usr/src/contrib/openpam/doc/man/pam_setcred.3 > pam_setcred.3.gz
--- all_subdir_lib/ncurses ---
--- all_subdir_lib/ncurses/form ---
--- fld_dup.po ---
cc -target x86_64-unknown-freebsd12.0 
--sysroot=/usr/obj/usr/src/amd64.amd64/tmp 
-B/usr/obj/usr/src/amd64.amd64/tmp/usr/bin -pg  -O2 -pipe -I. 
-I/usr/obj/usr/src/amd64.amd64/lib/ncurses/ncurses 
-I/usr/src/lib/ncurses/ncurses -I/usr/src/lib/ncurses/ncurses 
-I/usr/src/contrib/ncurses/include -I/usr/src/contrib/ncurses/ncurses 
-Wall -DNDEBUG -DHAVE_CONFIG_H -I/usr/src/contrib/ncurses/form 
-I/usr/src/contrib/ncurses/menu   -g -MD  -MF.depend.fld_dup.po 
-MTfld_dup.po -std=gnu99 -fstack-protector-strong -Wsystem-headers -Werror 
-Wall -Wno-format-y2k -W -Wno-unused-parameter -Wstrict-prototypes 
-Wmissing-prototypes -Wpointer-arith -Wno-uninitialized -Wno-pointer-sign 
-Wno-empty-body -Wno-string-plus-int -Wno-unused-const-variable 
-Wno-tautological-compare -Wno-unused-value -Wno-parentheses-equality 
-Wno-unused-function -Wno-enum-conversion -Wno-unused-local-typedef 
-Wno-address-of-packed-member  -Qunused-arguments  -c 
/usr/src/contrib/ncurses/form/fld_dup.c -o fld_dup.po
--- all_subdir_lib/libpam ---
--- pam_setenv.3.gz ---
--- all_subdir_lib/libcasper ---
cc: error: linker command failed with exit code 1 (use -v to see 
invocation)
*** [cap_sysctl] Error code 1

make[6]: stopped in /usr/src/lib/libcasper/services/cap_sysctl
1 error

make[6]: stopped in /usr/src/lib/libcasper/services/cap_sysctl
*** [all_subdir_lib/libcasper/services/cap_sysctl] Error code 2

make[5]: stopped in /usr/src/lib/libcasper/services
1 error

make[5]: stopped in /usr/src/lib/libcasper/services
--- all_subdir_lib/libpam ---
gzip -cn /usr/src/contrib/openpam/doc/man/pam_setenv.3 > pam_setenv.3.gz
--- all_subdir_lib/libcasper ---
*** [all_subdir_lib/libcasper/services] Error code 2

make[4]: stopped in /usr/src/lib/libcasper
1 error

make[4]: stopped in /usr/src/lib/libcasper
--- all_subdir_lib/libpam ---
A failure has been detected in another branch of the parallel make
--- all_subdir_lib/libcasper ---
*** [all_subdir_lib/libcasper] Error code 2

make[3]: stopped in /usr/src/lib
--- all_subdir_lib/libpam ---

make[5]: stopped in /usr/src/lib/libpam/libpam
*** [all_subdir_lib/libpam/libpam] Error code 2

make[4]: stopped in /usr/src/lib/libpam
1 error

make[4]: stopped in /usr/src/lib/libpam
*** [all_subdir_lib/libpam] Error code 2

make[3]: stopped in /usr/src/lib
--- all_subdir_lib/ncurses ---
A failure has been detected in another branch of the parallel make

make[5]: stopped in /usr/src/lib/ncurses/form
*** [all_subdir_lib/ncurses/form] Error code 2

make[4]: stopped in /usr/src/lib/ncurses
--- all_subdir_lib/libarchive ---
A failure has been detected in another branch of the parallel make

make[4]: stopped in /usr/src/lib/libarchive
*** [all_subdir_lib/libarchive] Error code 2

make[3]: stopped in /usr/src/lib
--- all_subdir_lib/ncurses ---
--- all_subdir_lib/ncurses/menu ---
A failure has been detected in another branch of the parallel make

make[5]: stopped in /usr/src/lib/ncurses/menu
*** [all_subdir_lib/ncurses/menu] Error code 2

make[4]: stopped in /usr/src/lib/ncurses
--- all_subdir_lib/ncurses/ncursesw ---
A failure has been detected in another branch of the parallel make

make[5]: stopped in /usr/src/lib/ncurses/ncursesw
*** [all_subdir_lib/ncurses/ncursesw] Error code 2

make[4]: stopped in /usr/src/lib/ncurses
3 errors

make[4]: stopped in /usr/src/lib/ncurses
*** [all_subdir_lib/ncurses] Error code 2

make[3]: stopped in /usr/src/lib
--- all_subdir_lib/libprocstat ---
A failure has been detected in another branch of the parallel make

make[4]: stopped in /usr/src/lib/libprocstat
*** [all_subdir_lib/libprocstat] Error code 2

make[3]: stopped in /usr/src/lib
--- all_subdir_lib/libunbound ---
A failure has been detected in another branch of the parallel make

make[4]: stopped in /usr/src/lib/libunbound
*** [all_subdir_lib/libunbound] Error code 2

make[3]: stopped in /usr/src/lib
--- all_subdir_lib/atf ---
A failure has been detected in another branch of the parallel make

make[5]: stopped in /usr/src/lib/atf/libatf-c++
*** [all_subdir_lib/atf/libatf-c++] Error code 2

make[4]: stopped in /usr/src/lib/atf
1 error

make[4]: stopped in /usr/src/lib/atf
*** [all_subdir_lib/atf] Error code 2

make[3]: stopped in /usr/src/lib
--- all_subdir_lib/libsqlite3 ---
A failure has been detected in another branch of the parallel make

make[4]: stopped in /usr/src/lib/libsqlite3
*** [all_subdir_lib/libsqlite3] Error code 2

make[3]: stopped in /usr/src/lib
8 errors

make[3]: stopped in /usr/src/lib
*** [all_subdir_lib] Error code 2

make[2]: stopped in /usr/src
1 error

make[2]: stopped in /usr/src
*** [everything] Error code 2

make[1]: stopped in /usr/src
1 error

make[1]: stopped in /usr/src
*** [buildworld] Error code 2

make: stopped in /usr/src
1 error

make: stopped in /usr/src