[clang][ssaf] Speculative fix of unittest build (#171720)
https://github.com/llvm/llvm-project/pull/169131
Should fix:
ASTEntityMappingTest.cpp.o: undefined reference to symbol
'_ZN4llvm3omp27isAllowedClauseForDirectiveENS0_9DirectiveENS0_6ClauseEj'
https://lab.llvm.org/buildbot/#/builders/10/builds/18851
