Functionally revert "config: disable thread safety analysis on COFF".

We don't use shared libraries on Windows anyway, so this shouldn't hurt
us, even if the bug in clang hasn't been fixed since the commit went in
two years ago.

Bug: http://b/124392080
Change-Id: Id562ac2bb64f1a384caa1553d2eeddd8371cf2ba
1 file changed