Fix thunks.cpp test, don't FileCheck for anon namespace id

The anon namespace id is a hash of the main input path to the compiler,
which varies in the test suite because the input path is absolute.

llvm-svn: 371277

clang/test/CodeGenCXX/thunks.cpp

@@ -148,7 +148,7 @@ namespace Test4B {
   }
 }
 // Not sure why this isn't delayed like in Itanium.
-// WIN64-LABEL: define internal void @"?f@C@?A0xAEF74CE7@Test4B@@UEAAXXZ"(
+// WIN64-LABEL: define internal void @"?f@C@?A{{.*}}@Test4B@@UEAAXXZ"(
 
 namespace Test5 {