clang-tidy: Don't repeat list of all checks in three places.

Instead, put all checks in a cmake variable and reference this.

Also, make clangd use the the ClangTidyForceLinker.h header instead
of duplicating the list of modules -- the duplicate copy was missing
the new "darwin" checker added in r373065.

Differential Revision: https://reviews.llvm.org/D68132

llvm-svn: 373082