message: build: upgrade yarn to 0.24.6
diff: @@ -36,7 +36,7 @@ fi
  setEnvVar NODE_VERSION 6.9.5
  setEnvVar NPM_VERSION 3.10.7 # do not upgrade to >3.10.8 unless https://github.com/npm/npm/issues/14042 is resolved
  -setEnvVar YARN_VERSION 0.21.3
  +setEnvVar YARN_VERSION 0.24.6
  setEnvVar CHROMIUM_VERSION 464641 # Chrome 59 linux stable, see https://www.chromium.org/developers/calendar
  setEnvVar SAUCE_CONNECT_VERSION 4.3.11
  setEnvVar PROJECT_ROOT $(cd ${thisDir}/../..; pwd)
  