[clang-tidy][modernize]: don't forget to actually link to Tooling.

Fixes build for me:

[1/5] Linking CXX shared library lib/libclangTidyModernizeModule.so.7svn
FAILED: lib/libclangTidyModernizeModule.so.7svn
<...>
/usr/local/bin/ld.lld: error: undefined symbol: clang::tooling::fixit::internal::getText(clang::SourceRange, clang::ASTContext const&)
>>> referenced by UseAutoCheck.cpp
>>>               tools/clang/tools/extra/clang-tidy/modernize/CMakeFiles/clangTidyModernizeModule.dir/UseAutoCheck.cpp.o:(clang::tidy::modernize::UseAutoCheck::replaceExpr(clang::DeclStmt const*, clang::ASTContext*, llvm::function_ref<clang::QualType (clang::Expr const*)>, llvm::StringRef))


Refs. D45405, rL329730.

llvm-svn: 329750