Fix test so it works the same way on 32-bit and 64-bit.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160415 91177308-0d34-0410-b5e6-96231b3b80d8

test/SemaCXX/constant-expression.cpp

@@ -115,7 +115,7 @@ int array2[recurse2]; // expected-warning {{variable length array}} expected-war
 namespace FloatConvert {
   typedef int a[(int)42.3];
   typedef int a[(int)42.997];
-  typedef int b[(int)4e10]; // expected-warning {{variable length}} expected-warning {{size of static array must be an integer constant expression}}
+  typedef int b[(long long)4e20]; // expected-warning {{variable length}} expected-error {{variable length}} expected-warning {{'long long' is an extension}}
 }
 
 // PR12626