message: Add required env variables to the tools test script on macOS.
diff: @@ -4,6 +4,10 @@ set -euo pipefail
  cd ${KOKORO_ARTIFACTS_DIR}/git/tink
  cd tools
  +export XCODE_VERSION=11.3
  +export DEVELOPER_DIR="/Applications/Xcode_${XCODE_VERSION}.app/Contents/Developer"
  +export ANDROID_HOME="/Users/kbuilder/Library/Android/sdk"
  +
  # TODO(b/155225382): Avoid modifying the sytem Python installation.
  pip3 install --user protobuf
  