Update tests to use %clang_cc1 instead of 'clang-cc' or 'clang -cc1'.

Update tests to use %clang_cc1 instead of 'clang-cc' or 'clang -cc1'.
 - This is designed to make it obvious that %clang_cc1 is a "test variable"
   which is substituted. It is '%clang_cc1' instead of '%clang -cc1' because it
   can be useful to redefine what gets run as 'clang -cc1' (for example, to set
   a default target).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@91446 91177308-0d34-0410-b5e6-96231b3b80d8