Broken toolchain?

[Paul Beard]

Cleaning up a mess here and needing to rebuild a lot of ports. I keep seeing this error: 

undefined reference to `_sem_timedwait’

More context: 
cc -o perl -pthread -Wl,-E  -fstack-protector-strong -L/usr/local/lib -Wl,-R/usr/local/lib/perl5/5.28/mach/CORE maindtrace/perlmain.o dtrace_main.o  libperl.so.5.28.2 `cat ext.libs` -lpthread -lm -lcrypt -lutil
libperl.so.5.28.2: undefined reference to `_sem_timedwait'
libperl.so.5.28.2: undefined reference to `_sem_getvalue'
libperl.so.5.28.2: undefined reference to `_sem_destroy'
libperl.so.5.28.2: undefined reference to `_sem_wait'
libperl.so.5.28.2: undefined reference to `_sem_init'
libperl.so.5.28.2: undefined reference to `_sem_post'
libperl.so.5.28.2: undefined reference to `_sem_trywait'
cc: error: linker command failed with exit code 1 (use -v to see invocation)

What am I missing or what’s broke? 

cc -v
FreeBSD clang version 8.0.0 (tags/RELEASE_800/final 356365) (based on LLVM 8.0.0)
Target: i386-unknown-freebsd11.2
Thread model: posix
InstalledDir: /usr/bin

Kernel is hours old, FreeBSD 11.2