message: Do not update config.mk if configuration is unchanged
  This will prevent unnecessary rebuilds
diff: @@ -460,6 +460,7 @@ find_android_ndk()
  }
  CONFIG_MK="src/config.mk"
  +CONFIG_TMP="src/config.tmp"
  require_config()
  {
  @@ -690,7 +691,7 @@ case "$MODE" in
  android_ndk_home="$(find_android_ndk)" || android_ndk_home="none"
  fi
  - cat >"$CONFIG_MK" <<EOF
  + cat >"$CONFIG_TMP" <<EOF
  CONFIG_VERSION = ${CONFIG_VERSION}
  REALM_VERSION = $realm_version
  INSTALL_PREFIX = $install_prefix
  @@ -716,8 +717,14 @@ TVOS_SDKS = ${tvos_sdks:-none}
  TVOS_SDKS_AVAIL = $tvos_sdks_avail
  ANDROID_NDK_HOME = $android_ndk_home
  EOF
  + CONFIG_STATUS="Existing"
  + if ! [ -e $CONFIG_MK ] || [ "$(diff $CONFIG_TMP $CONFIG_MK)" ]; then
  + cp $CONFIG_TMP $CONFIG_MK
  + CONFIG_STATUS="New"
  + fi
  + rm $CONFIG_TMP
  if ! [ "$INTERACTIVE" ]; then
  - echo "New configuration in $CONFIG_MK:"
  + echo "$CONFIG_STATUS configuration in $CONFIG_MK:"
  cat "$CONFIG_MK" | sed 's/^/ /' || exit 1
  echo "Done configuring"
  fi
  