[flang] Update build config for PowerPC (#294)

Author: kkwli

buildbot/osuosl/master/config/builders.py

@@ -2417,7 +2417,7 @@
     'builddir': 'ppc64le-flang-rhel-clang-build',
     'factory' : UnifiedTreeBuilder.getCmakeWithNinjaBuildFactory(
                     clean=True,
-                    depends_on_projects=['llvm', 'mlir', 'clang', 'flang'],
+                    depends_on_projects=['llvm', 'mlir', 'clang', 'flang','openmp'],
                     checks=['check-flang'],
                     extra_configure_args=[
                         '-DLLVM_TARGETS_TO_BUILD=PowerPC',