Fix linking of omp_foreign_thread_team_reuse test on FreeBSD

Summary:
On FreeBSD, linking the misc_bugs/omp_foreign_thread_team_reuse.c test
case fails with:

   /usr/local/bin/ld: /tmp/omp_foreign_thread_team_reuse-c5e71b.o: undefined reference to symbol 'pthread_create@@FBSD_1.0'

This is because the program is linked without `-lpthread`.  Since the
%libomp-compile-and-run macro does not allow that option to be added to
the compile command line, split it up and add the required `-lpthread`
between %libomp-compile and %libomp-run.

Reviewers: jlpeyton, hfinkel, Hahnfeld

Subscribers: Hahnfeld, emaste, openmp-commits

Differential Revision: https://reviews.llvm.org/D23084

llvm-svn: 278036