[clangd] Mention whether compile flags were inferred in check mode

That way when looking at logs it's clear whether diagnostics are a
result of compile flags mismatch.

Differential Revision: https://reviews.llvm.org/D130228

clang-tools-extra/clangd/tool/Check.cpp

@@ -111,7 +111,9 @@ public:
 
     if (auto TrueCmd = CDB->getCompileCommand(File)) {
       Cmd = std::move(*TrueCmd);
-      log("Compile command from CDB is: {0}", printArgv(Cmd.CommandLine));
+      log("Compile command {0} is: {1}",
+          Cmd.Heuristic.empty() ? "from CDB" : Cmd.Heuristic,
+          printArgv(Cmd.CommandLine));
     } else {
       Cmd = CDB->getFallbackCommand(File);
       log("Generic fallback command is: {0}", printArgv(Cmd.CommandLine));