libgo: don't copy semt into runtime.inc

https://gcc.gnu.org/PR81449 reports a problem with the definition semt
in runtime.inc on some systems. Since the C code in libgo/runtime
doesn't need semt, just don't copy it into runtime.inc.

Change-Id: I0e87fd737b19d8217a603e50aeac259122ed021c
Reviewed-on: https://go-review.googlesource.com/48593
Reviewed-by: Than McIntosh <thanm@google.com>
3 files changed