Adding RUN lines.

llvm-svn: 17532
diff --git a/llvm/test/Regression/CFrontend/2002-07-30-UnionTest.c b/llvm/test/Regression/CFrontend/2002-07-30-UnionTest.c
index ffb1d5b..634ed3f 100644
--- a/llvm/test/Regression/CFrontend/2002-07-30-UnionTest.c
+++ b/llvm/test/Regression/CFrontend/2002-07-30-UnionTest.c
@@ -1,3 +1,5 @@
+// RUN: %llvmgcc -S %s -o - | llvm-as -f -o /dev/null
+
 union X;
 struct Empty {};
 union F {};