cmd/gomote: add debug print showing actual Go bootstrap toolchain

This only affects legacy mode (which we use today)
but it is still useful for now.

Change-Id: Id8324b0846ccf8cb1bc7ab8b8aabc18585ed355d
Reviewed-on: https://go-review.googlesource.com/c/build/+/419991
Reviewed-by: Carlos Amedee <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Russ Cox <[email protected]>

Author: rsc

Diff for: cmd/gomote/push.go

@@ -93,9 +93,9 @@ func legacyPush(args []string) error {
 
 	if !haveGo14 {
 		if u := conf.GoBootstrapURL(buildEnv); u != "" {
-			log.Printf("installing go1.4")
+			log.Printf("installing go1.4 from %s", u)
 			if dryRun {
-				log.Printf("(Dry-run) Would have pushed go1.4")
+				log.Printf("(Dry-run) Would have pushed go1.4 from %s", u)
 			} else {
 				if err := bc.PutTarFromURL(ctx, u, "go1.4"); err != nil {
 					return err