[clangd] Upgrade vlog() to log() for preamble build stats

[adamcz]

Summary

This is very useful information for better understanding performance and
preamble builds don't happen that often, so it's not that spammy.

[kadircet]

clang-tools-extra/clangd/Preamble.cpp

555

what about also moving this log into TUScheduler.cpp::reportPreamble, in which we can also log whether this is a "first preamble" or not?

[adamcz]

clang-tools-extra/clangd/Preamble.cpp

555

I considered that, but this isn't structured log or something you'd process automatically and it's already clear from context in that log file if it's first build or rebuild. I think it's simpler to keep the log line here, to match the error line below.

If you have a use case for this information let me know and I'll update this change, otherwise I'll just go with the simple solution.

clang-tools-extra/clangd/Preamble.cpp

buildPreamble(PathRef FileName, CompilerInvocation CI,
 
   if (Stats != nullptr) {
     Stats->TotalBuildTime = PreambleTimer.getTime();
     Stats->FileSystemTime = TimedFS->getTime();
     Stats->SerializedSize = BuiltPreamble ? BuiltPreamble->getSize() : 0;
   }
 
   if (BuiltPreamble) {
-    vlog("Built preamble of size {0} for file {1} version {2} in {3} seconds",
+    log("Built preamble of size {0} for file {1} version {2} in {3} seconds",
          BuiltPreamble->getSize(), FileName, Inputs.Version,
          PreambleTimer.getTime());
     std::vector<Diag> Diags = PreambleDiagnostics.take();
     auto Result = std::make_shared<PreambleData>(std::move(*BuiltPreamble));
     Result->Version = Inputs.Version;
     Result->CompileCommand = Inputs.CompileCommand;
     Result->Diags = std::move(Diags);
     Result->Includes = CapturedInfo.takeIncludes();