eliminate some random .ll file outputs


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@63117 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CodeGen/union.c b/test/CodeGen/union.c
index 9d82f4f..4b09a84 100644
--- a/test/CodeGen/union.c
+++ b/test/CodeGen/union.c
@@ -1,4 +1,4 @@
-// RUN: clang %s -emit-llvm -o %t
+// RUN: clang %s -emit-llvm -o -
 
 union u_tag {
   int a;