[clang][OpenMP] Fix build when using libgomp

Summary: rL356570 introduced a test which only passes with the default openmp library, libomp, and fails with other openmp libraries, such as libgomp. Explicitly choose libomp.

Reviewers: lebedev.ri

Subscribers: guansong, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D59609

llvm-svn: 356614

clang/unittests/AST/OMPStructuredBlockTest.cpp

@@ -55,7 +55,7 @@ PrintedOMPStmtMatches(StringRef Code, const T &NodeMatch,
                       StringRef ExpectedPrinted,
                       PolicyAdjusterType PolicyAdjuster = None) {
   std::vector<std::string> Args = {
-      "-fopenmp",
+      "-fopenmp=libomp",
   };
   return PrintedStmtMatches(Code, Args, NodeMatch, ExpectedPrinted,
                             PolicyAdjuster);