Phrase compile time assert in standard way.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@85079 91177308-0d34-0410-b5e6-96231b3b80d8

test/Sema/vector-init.c

@@ -26,5 +26,5 @@ float f1(void) {
 
 // PR5265
 typedef float __attribute__((ext_vector_type (3))) float3;
-int test2[(sizeof(float3) == sizeof(float4))*2-1];
+int test2[sizeof(float3) == sizeof(float4) ? 1 : -1];