Fix an incorrect union layout assert. Fixes PR6164.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@94754 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CodeGen/union.c b/test/CodeGen/union.c
index b40a405..1883ca6 100644
--- a/test/CodeGen/union.c
+++ b/test/CodeGen/union.c
@@ -39,3 +39,6 @@
 union RR {_Bool a : 1;} RRU;
 int RRF(void) {return RRU.a;}
 
+// PR6164
+typedef union T0 { unsigned int : 0; } T0;
+T0 t0;