Generate build timing metrics to proto format file

Test: Dumped the text formated based metrics file to out dir,
and checked the file.
Bug: b/63815990

Change-Id: Iff476f72a0be74eb53b6b26ef468d11c0f24a404
diff --git a/ui/build/path.go b/ui/build/path.go
index 8260ff9..ee72cfd 100644
--- a/ui/build/path.go
+++ b/ui/build/path.go
@@ -25,6 +25,7 @@
 	"github.com/google/blueprint/microfactory"
 
 	"android/soong/ui/build/paths"
+	"android/soong/ui/metrics"
 )
 
 func parsePathDir(dir string) []string {
@@ -57,7 +58,7 @@
 		return
 	}
 
-	ctx.BeginTrace("path")
+	ctx.BeginTrace(metrics.RunSetupTool, "path")
 	defer ctx.EndTrace()
 
 	origPath, _ := config.Environment().Get("PATH")