head -r351102 amd64 rebuilding itself but via devel/xtoolchain-llvm90 ( rc2: ports head -r509054 ) fails for boot2.out: ld.lld: error: undefined symbol: __ashldi3

My attempt to have -r351102 rebuild itself via devel/llvm90 (rc2)
got:

--- all_subdir_stand ---
--- boot2.out ---
ld.lld: error: undefined symbol: __ashldi3
>>> referenced by ufsread.c:234 (/usr/src/stand/libsa/ufsread.c:234)
>>>               boot2.o:(fsread)
>>> referenced by ufsread.c:270 (/usr/src/stand/libsa/ufsread.c:270)
>>>               boot2.o:(fsread)
>>> referenced by ufsread.c:295 (/usr/src/stand/libsa/ufsread.c:295)
>>>               boot2.o:(fsread)
>>> referenced by ufsread.c:297 (/usr/src/stand/libsa/ufsread.c:297)
>>>               boot2.o:(fsread)
*** [boot2.out] Error code 1

make[5]: stopped in /usr/src/stand/i386/boot2
.ERROR_TARGET='boot2.out'
.ERROR_META_FILE='/usr/obj/amd64_xtoolchain-llvm/amd64.amd64/usr/src/amd64.amd64/stand/i386/boot2/boot2.out.meta'
.MAKE.LEVEL='5'
MAKEFILE=''
.MAKE.MODE='meta missing-filemon=yes missing-meta=yes silent=yes verbose'
_ERROR_CMD='/usr/local/llvm90/bin/ld.lld -m elf_i386_fbsd -static -N --gc-sections -Ttext 0x2000 -o boot2.out /usr/obj/amd64_xtoolchain-llvm/amd64.amd64/usr/src/amd64.amd64/stand/i386/btx/lib/crt0.o boot2.o sio.o;'
.CURDIR='/usr/src/stand/i386/boot2'
.MAKE='make'
.OBJDIR='/usr/obj/amd64_xtoolchain-llvm/amd64.amd64/usr/src/amd64.amd64/stand/i386/boot2'
.TARGETS='all'
DESTDIR='/usr/obj/amd64_xtoolchain-llvm/amd64.amd64/usr/src/amd64.amd64/tmp'
LD_LIBRARY_PATH=''
MACHINE='amd64'
MACHINE_ARCH='amd64'
MAKEOBJDIRPREFIX=''
MAKESYSPATH='/usr/src/share/mk'
MAKE_VERSION='20181221'
PATH='/usr/obj/amd64_xtoolchain-llvm/amd64.amd64/usr/src/amd64.amd64/tmp/usr/sbin:/usr/obj/amd64_xtoolchain-llvm/amd64.amd64/usr/src/amd64.amd64/tmp/usr/bin:/usr/obj/amd64_xtoolchain-llvm/amd64.amd64/usr/src/amd64.amd64/tmp/legacy/usr/sbin:/usr/obj/amd64_xtoolchain-llvm/amd64.amd64/usr/src/amd64.amd64/tmp/legacy/usr/bin:/usr/obj/amd64_xtoolchain-llvm/amd64.amd64/usr/src/amd64.amd64/tmp/legacy/bin::/sbin:/bin:/usr/sbin:/usr/bin'
SRCTOP='/usr/src'
OBJTOP='/usr/obj/amd64_xtoolchain-llvm/amd64.amd64/usr/src/amd64.amd64'
.MAKE.MAKEFILES='/usr/src/share/mk/sys.mk /usr/src/share/mk/local.sys.env.mk /usr/src/share/mk/src.sys.env.mk /root/src.configs/src.conf.amd64-xtoolchain-llvm.amd64-host /usr/src/share/mk/bsd.mkopt.mk /usr/src/share/mk/src.sys.obj.mk /usr/src/share/mk/auto.obj.mk /usr/src/share/mk/bsd.suffixes.mk /root/src.configs/make.conf /usr/src/share/mk/local.sys.mk /usr/src/share/mk/src.sys.mk /dev/null /usr/src/stand/i386/boot2/Makefile /usr/src/share/mk/bsd.init.mk /usr/src/share/mk/bsd.opts.mk /usr/src/share/mk/bsd.cpu.mk /usr/src/share/mk/local.init.mk /usr/src/share/mk/src.init.mk /usr/src/stand/i386/boot2/../Makefile.inc /usr/src/share/mk/bsd.linker.mk /usr/src/stand/i386/boot2/../../Makefile.inc /usr/src/stand/i386/boot2/../../defs.mk /usr/src/share/mk/src.opts.mk /usr/src/share/mk/bsd.own.mk /usr/src/share/mk/bsd.compiler.mk /usr/src/share/mk/bsd.compiler.mk /usr/src/share/mk/bsd.prog.mk /usr/src/share/mk/bsd.libnames.mk /usr/src/share/mk/src.libnames.mk /usr/src/share/mk/bsd.nls.mk /usr/src/share/mk/bsd.confs.mk /usr/src/share/mk/bsd.files.mk /usr/src/share/mk/bsd.dirs.mk /usr/src/share/mk/bsd.incs.mk /usr/src/share/mk/bsd.links.mk /usr/src/share/mk/bsd.man.mk /usr/src/share/mk/bsd.dep.mk /usr/src/share/mk/bsd.clang-analyze.mk /usr/src/share/mk/bsd.obj.mk /usr/src/share/mk/bsd.subdir.mk /usr/src/share/mk/bsd.sys.mk'
.PATH='. /usr/src/stand/i386/boot2'
1 error

FYI:

# uname -apKU
FreeBSD FBSDFHUGE 13.0-CURRENT FreeBSD 13.0-CURRENT #29 r351102M: Thu Aug 15 14:22:00 PDT 2019     markmi_at_FBSDFHUGE:/usr/obj/amd64_clang/amd64.amd64/usr/src/amd64.amd64/sys/GENERIC-NODBG  amd64 amd64 1300039 1300039


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)