[clang-tidy] Fix build with -DBUILD_SHARED_LIB=ON

Summary: This fixes build failures with `-DBUILD_SHARED_LIB=ON` after D67419.

Reviewers: NoQ

Subscribers: mgorny, xazax.hun, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D67473

llvm-svn: 371706