Try to fix another profile test

Another CFG optimisation patch (280364) has broken bad profile tests, and this
is a similar attempt to fix the test without changing the semantics.

llvm-svn: 280373

compiler-rt/test/profile/Inputs/comdat_rename.h

@@ -9,5 +9,5 @@ struct FOO {
       }
   }
   int a;
-  int b;
+  int volatile b;
 };