message: Install the Android build tools version needed by Gradle.
  Only doing this step in Kokoro environments as we want to avoid making system
  changes unless we're certain we're operating in an ephemeral envioronment.
diff: @@ -21,6 +21,9 @@ set -e
  # Display commands to stderr.
  set -x
  +# Version of Android build-tools required for gradle.
  +readonly ANDROID_BUILD_TOOLS_VERSION="28.0.3"
  +
  test_java_snapshot() {
  local -r test_tmpdir="$(mktemp -d)"
  mkdir -p "${test_tmpdir}"
  @@ -49,6 +52,13 @@ test_java_snapshot() {
  }
  test_android_snapshot() {
  + # Only in the Kokoro environment.
  + if [[ -n "${KOKORO_ROOT}" ]]; then
  + yes | "${ANDROID_HOME}/tools/bin/sdkmanager" \
  + "build-tools;${ANDROID_BUILD_TOOLS_VERSION}"
  + yes | "${ANDROID_HOME}/tools/bin/sdkmanager" --licenses
  + fi
  +
  ./examples/android/helloworld/gradlew -p ./examples/android/helloworld build
  }
  