v.io/jiri/profiles/commandline: issue a warning when using a target with --all-targets.

Change-Id: I95da944caedffe082ab39613a039eb0dee6e78a9
diff --git a/profiles/commandline/driver.go b/profiles/commandline/driver.go
index 94b8380..171e1f1 100644
--- a/profiles/commandline/driver.go
+++ b/profiles/commandline/driver.go
@@ -647,7 +647,7 @@
 		return err
 	}
 	if allFlag && targetFlag.IsSet() {
-		return fmt.Errorf("don't specify a target (%v) in conjunction with --all-targets", targetFlag)
+		fmt.Fprintf(ctx.Stdout(), "ignore target (%v) when used in conjunction with --all-targets\n", targetFlag)
 	}
 	if allFlag {
 		for _, name := range args {