[clang] [clang][DependencyScanning] Logging Dependency Scanning Events (PR #195896)

[Michael Spencer via cfe-commits]

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@@ -89,6 +90,22 @@ bool DependencyScanningWorker::computeDependencies(
       return true;
     }
 
+    {
+      auto LogLine = Service.getLogger().log();
+      LogLine << "starting scanning command:";
+      for (const auto &C : Cmd) {
+        LogLine << " " << C;
+      }
+    }
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Bigcheese wrote:

Did you check what the overhead is when logging is disabled? My expectation is that stuff like this loop still runs, but each `operator <<` exits early.

https://github.com/llvm/llvm-project/pull/195896