buildworld failure: pfvar.h:44 #include <netpfil/pf/pf.h> not found

===> sbin/ifconfig (depend)
rm -f .depend
CC='/path/to/clang --sysroot=/usr/obj/usr/src/tmp -B/usr/obj/usr/src/tmp/usr/bin' mkdep -f .depend -a    -DINET -DNDEBUG -std=gnu99   /usr/src/sbin/ifconfig/ifconfig.c /usr/src/sbin/ifconfig/af_link.c /usr/src/sbin/ifconfig/af_inet.c /usr/src/sbin/ifconfig/af_atalk.c /usr/src/sbin/ifconfig/ifclone.c /usr/src/sbin/ifconfig/ifmac.c /usr/src/sbin/ifconfig/ifmedia.c /usr/src/sbin/ifconfig/iffib.c /usr/src/sbin/ifconfig/ifvlan.c /usr/src/sbin/ifconfig/ifgre.c /usr/src/sbin/ifconfig/ifgif.c /usr/src/sbin/ifconfig/ifieee80211.c /usr/src/sbin/ifconfig/regdomain.c /usr/src/sbin/ifconfig/carp.c /usr/src/sbin/ifconfig/ifgroup.c /usr/src/sbin/ifconfig/ifpfsync.c /usr/src/sbin/ifconfig/ifbridge.c /usr/src/sbin/ifconfig/iflagg.c
In file included from /usr/src/sbin/ifconfig/ifpfsync.c:35:
/usr/obj/usr/src/tmp/usr/include/net/pfvar.h:44:10: fatal error:
       'netpfil/pf/pf.h' file not found
#include <netpfil/pf/pf.h>
          ^

/usr/obj was clean.

The environment contains, notably:
CC=/path/to/clang
CXX=/path/to/clang++
CPP=/path/to/clang-cpp
WITHOUT_SSP=1

/etc/make.conf is:
CPUTYPE?=native
CXXFLAGS+= -stdlib=libc++
KERNCONF=CUSTOM
NO_CLEAN=1
NO_KERNELCLEAN=1
NO_MODULES=1
MALLOC_PRODUCTION=1
WITHOUT_SSP=1

/etc/src.conf is:
WITHOUT_ACCT=1
WITHOUT_ACPI=1
WITHOUT_AMD=1
WITHOUT_APM=1
WITHOUT_ASSERT_DEBUG=1
WITHOUT_AT=1
WITHOUT_ATF=1
WITHOUT_ATM=1
WITHOUT_AUDIT=1
WITHOUT_AUTHPF=1
WITHOUT_BLUETOOTH=1
WITHOUT_BSNMP=1
WITHOUT_CALENDAR=1
WITHOUT_CAPSICUM=1
WITHOUT_CDDL=1
WITHOUT_CLANG=1
WITHOUT_CPP=1
WITHOUT_CROSS_COMPILER=1
WITHOUT_CTM=1
WITHOUT_DICT=1
WITHOUT_ED_CRYPTO=1
WITHOUT_EXAMPLES=1
WITHOUT_FDT=1
WITHOUT_FLOPPY=1
WITHOUT_FORMAT_EXTENSIONS=1
WITHOUT_FREEBSD_UPDATE=1
WITHOUT_GAMES=1
WITHOUT_GCC=1
WITHOUT_GCOV=1
WITHOUT_GDB=1
WITHOUT_GNUCXX=1
WITHOUT_GPIB=1
WITHOUT_GPIO=1
WITHOUT_HESIOD=1
WITHOUT_HTML=1
WITHOUT_INET6=1
WITHOUT_IPFILTER=1
WITHOUT_IPFW=1
WITHOUT_IPX=1
WITHOUT_JAIL=1
WITHOUT_KDUMP=1
WITHOUT_KERNEL_SYMBOLS=1
WITHOUT_KVM=1
WITHOUT_LDNS=1
WITHOUT_LEGACY_CONSOLE=1
WITHOUT_LOCALES=1
WITHOUT_LOCATE=1
WITHOUT_LPR=1
WITHOUT_MAIL=1
WITHOUT_NDIS=1
WITHOUT_NETGRAPH=1
WITHOUT_NLS=1
WITHOUT_NLS_CATALOGS=1
WITHOUT_NTP=1
WITHOUT_PC_SYSINSTALL=1
WITHOUT_PF=1
WITHOUT_PMC=1
WITHOUT_PORTSNAP=1
WITHOUT_PPP=1
WITHOUT_PROFILE=1
WITHOUT_QUOTAS=1
WITHOUT_RCMDS=1
WITHOUT_RCS=1
WITHOUT_RESCUE=1
WITHOUT_SENDMAIL=1
WITHOUT_SHAREDOCS=1
WITHOUT_SOURCELESS=1
WITHOUT_SSP=1
WITHOUT_SYSINSTALL=1
WITHOUT_TELNET=1
WITHOUT_UNBOUND=1
WITHOUT_WIRELESS=1
WITHOUT_WPA_SUPPLICANT_EAPOL=1
WITHOUT_ZFS=1
WITH_BSD_GREP=1
WITH_SVN=1