fix print of total elapsed time

common.sh

 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Common constants for build scripts
 # This must evaluate properly for both /bin/bash and /bin/sh
 
 # All scripts should die on error unless commands are specifically excepted
 # by prefixing with '!' or surrounded by 'set +e' / 'set -e'.
 # TODO: Re-enable this once shflags is less prone to dying.
@@ skipping 436 matching lines @@
 
 # Get current timestamp. Assumes common.sh runs at startup.
 start_time=$(date +%s)
 
 # Print time elsapsed since start_time.
 print_time_elapsed() {
   end_time=$(date +%s)
   elapsed_seconds="$(( $end_time - $start_time ))"
   minutes="$(( $elapsed_seconds / 60 ))"
   seconds="$(( $elapsed_seconds % 60 ))"
-  echo "Elapsed time: ${minutes}:${seconds}"
+  echo "Elapsed time: ${minutes}m${seconds}s"
 }