[pp-trace] Use ClangTool in pp-trace, NFC

Summary:
This patch partially reverts the commit rL356849.

Unfortunately, tooling::createExecutorFromCommandLineArgs doesn't
corperate well with our internal infrastructure, which leads failing
lit tests. We use ClangTool at the moment, until we find a better
solution to smooth it.

Reviewers: ioeric

Reviewed By: ioeric

Subscribers: jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D59764

llvm-svn: 356893