[clangd] Fix ExtractFunction dependencies

Summary: Without these dependencies, builds with `-DBUILD_SHARED_LIBS=ON` fail.

Reviewers: SureYeaah

Subscribers: mgorny, ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D66910

llvm-svn: 370273