dockerTools: disable compression in tarsum.go

Previously, tarsum would compress the (discarded) tarball produced.
That's a waste of CPU, and a waste of time.

pkgs/build-support/docker/tarsum.go

@@ -9,7 +9,7 @@ import (
 )
 
 func main() {
-	ts, err := tarsum.NewTarSum(os.Stdin, false, tarsum.Version1)
+	ts, err := tarsum.NewTarSum(os.Stdin, true, tarsum.Version1)
 	if err != nil {
 		fmt.Println(err)
 		os.Exit(1)