#     nonccl:       Disable nccl support.
#
#
# Remote build execution options (only configured to work with TF team projects for now.)
#     rbe_base:  General RBE options shared by all flavors.
#     rbe_linux: General RBE options used on all linux builds.
#     rbe_win_base:   General RBE options used on all Windows builds. Not to be used standalone.
#     rbe_win_clang:  Options specific to compiling using Clang.
#

				// curl -H "Metadata-Flavor: Google" 169.254.169.254/computeMetadata/v1/instance/service-accounts/default/identity
				opts := echo.CallOptions{
					Address: "169.254.169.254",
					Port:    echo.Port{ServicePort: 80},
					Scheme:  scheme.HTTP,
					HTTP: echo.HTTP{
						// TODO: detect which platform?
						Headers: headers.New().With("Metadata-Flavor", "Google").Build(),

    error_msg: (String) String with one and only one '%s'. Formatted with each
      invalid response upon check_success(input) failure.
    suppress_default_error: (Bool) Suppress the above error message in favor of
      one from the check_success function.
    resolve_symlinks: (Bool) Translate symbolic links into the real filepath.
    n_ask_attempts: (Integer) Number of times to query for valid input before