timespec_getres() has been declared in <time.h> and built into libc,
but never listed in a symbol map. It is therefore local to libc.so,
and dynamically linked callers fail to link.
Reviewed by: ziaee, fuz, des
Approved by: fuz (mentor)
Fixes: 9b5d724cad ("libc: Add timespec_getres(3) as per C23.")
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D60799