[libtooling] silence unavoidable warnings about unused variable
[libtooling] silence unavoidable warnings about unused variable

Summary: The warnings stem from a #include trick and are a necessary part of life.

Test Plan: `make -C libtooling` doesn't warn about these unused variables anymore.

Reviewers: akotulski, mathieubaudet

Reviewed By: mathieubaudet

Subscribers: martinoluca

Differential Revision: https://phabricator.fb.com/D2346314

Signature: t1:2346314:1439588422:daa99b7ef83b6362e212e93891cf15a38a3e02f2

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