buildworld question.

Apologies if this applies to STABLE 13, but git is involved...
buildworld is failing 4 minutes or so in.
would it be useful to re-git the /usr/src? 
Is there a way to run "make buildworld" for a LESS terse error result?
Any other 3rd method to debug the error?
..........................................................................................
/usr/local/bin/clang12 ..... -o machdep_ldisx.o
In file included from /usr/src/lib/libc/gdtoa/machdep_ldisx.c:45:
In file included from /usr/src/contrib/gdtoa/gdtoaimp.h:202:
In file included from /usr/src/include/pthread.h:49:
/usr/src/include/time.h: fatal error: 'sys/_clock_id.h' file not found
#include <sys/_clock_id.h>
.........................................................................
I also suspect the missing file might be a malformed missing
symlink instead...  because the file exists at least once. 
The error does not indicate from what [ 2nd ] subdir it, or a symlink, is missing ?? 

src.conf has several lines such as WITHOUT_CPP=yes, meant I think
to reduce build times if that matters.