[clangd] Log clang-tidy configuration, NFC

[hokein]

Summary

This is used for debugging purpose.

[jkorous]

LGTM

[sammccall]

This turns out to be excessively spammy in unit tests, can we change this to dlog()?

[hokein]

In D57057#1375249, @sammccall wrote:

This turns out to be excessively spammy in unit tests, can we change this to dlog()?

Sure, done in rL352485.

clangd/ClangdUnit.cpp

ParsedAST::build(std::unique_ptr<CompilerInvocation> CI,
   //  - matchers run only over the main-file top-level decls (and can't see
   //    ancestors outside this scope).
   // In practice almost all checks work well without modifications.
   std::vector<std::unique_ptr<tidy::ClangTidyCheck>> CTChecks;
   ast_matchers::MatchFinder CTFinder;
   llvm::Optional<tidy::ClangTidyContext> CTContext;
   {
     trace::Span Tracer("ClangTidyInit");
+    vlog("ClangTidy configuration for file {0}: {1}", MainInput.getFile(),
+         tidy::configurationAsText(ClangTidyOpts));
     tidy::ClangTidyCheckFactories CTFactories;
     for (const auto &E : tidy::ClangTidyModuleRegistry::entries())
       E.instantiate()->addCheckFactories(CTFactories);
     CTContext.emplace(llvm::make_unique<tidy::DefaultOptionsProvider>(
         tidy::ClangTidyGlobalOptions(), ClangTidyOpts));
     CTContext->setDiagnosticsEngine(&Clang->getDiagnostics());
     CTContext->setASTContext(&Clang->getASTContext());
     CTContext->setCurrentFile(MainInput.getFile());