message: Replace global starter flags with call-specific flags
  The earlier version of convenient default flags mistakenly applied --build_tests_only to normal "bazel build" calls, which broke pip.sh (and probably invalidated some other things). This resolves that problem by setting flags specific to "test" and "build" commands.
diff: @@ -127,17 +127,19 @@ NO_DOCKER_OPT_FLAG="--genrule_strategy=standalone"
  DO_DOCKER=1
  -BAZEL_CMD="bazel test"
  -BAZEL_BUILD_ONLY_CMD="bazel build"
  -BAZEL_CLEAN_CMD="bazel clean"
  -# Default flags:
  +# Helpful flags:
  # --test_summary=detailed: Tell us more about which targets are being built
  # --keep_going: Don't stop at the first failure; tell us all the failures
  # --build_tests_only: Don't build targets depended on by tests if the test is
  # disabled. Also saves some compilation time. Otherwise,
  # tries to build everything.
  -DEFAULT_BAZEL_CONFIGS="--test_summary=detailed --build_tests_only --keep_going"
  +BAZEL_TEST_FLAGS="--test_summary=detailed --build_tests_only --keep_going"
  +BAZEL_BUILD_FLAGS="--keep_going"
  +
  +BAZEL_CMD="bazel test ${BAZEL_TEST_FLAGS}"
  +BAZEL_BUILD_ONLY_CMD="bazel build ${BAZEL_BUILD_FLAGS}"
  +BAZEL_CLEAN_CMD="bazel clean"
  PIP_CMD="${CI_BUILD_DIR}/builds/pip.sh"
  PIP_TEST_TUTORIALS_FLAG="--test_tutorials"
  