On Solaris 2.5.1 using POSIX threads is controlled by either
_POSIX_C_SOURCE >= 199506L or _POSIX_PTHREAD_SEMANTICS
according to the getpwnam_r manpage.
Should the pthreads entry in the specs set _POSIX_PTHREAD_SEMANTICS
or should this be setup based on autoconf.
gcc/config/sparc/sol2.h:%{pthreads:-D_REENTRANT -D_PTHREADS} \