Merging r338757: ------------------------------------------------------------------------ r338757 | jlpeyton | 2018-08-02 21:13:07 +0200 (Thu, 02 Aug 2018) | 8 lines

[OpenMP] Fix doacross testing for gcc

This patch adds a test using the doacross clauses in OpenMP and removes gcc from
testing kmp_doacross_check.c which is only testing the kmp rather than the
gomp interface.

Differential Revision: https://reviews.llvm.org/D50014

llvm-svn: 338844