Don't check clang binary name, as it can be different in some test setups.

Summary: This unbreaks our internal build after these tests were turned on in r211738.

Reviewers: chandlerc

Reviewed By: chandlerc

Subscribers: benlangmuir, cfe-commits

Differential Revision: http://reviews.llvm.org/D4311

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@211887 91177308-0d34-0410-b5e6-96231b3b80d8