gn build: Fix clang-tidy build

Not depending on //clang/lib/StaticAnalyzer/Core and
//clang/lib/StaticAnalyzer/Frontend causes a linker error even if
ClangSACheckers are not supported.

Undefined symbols for architecture x86_64:
  "clang::ento::CreateAnalysisConsumer(clang::CompilerInstance&)", referenced from:
      clang::tidy::ClangTidyASTConsumerFactory::CreateASTConsumer(
              clang::CompilerInstance&, llvm::StringRef)
          in libclangTidy.a(libclangTidy.ClangTidy.o)

Patch from Mirko Bonadei <mbonadei@webrtc.org>!

Differential Revision: https://reviews.llvm.org/D57777

llvm-svn: 353244