The following options are understood:
       -h, --help
           Show help options and exit.
       --arch=ARCH
           The architecture to use. See flatpak --supported-arches for
           architectures supported by the host.
       -v, --var=RUNTIME
           Initialize var from the named runtime.
       -w, --writable-sdk
           Initialize /usr with a copy of the sdk, which is writable
           during flatpak build. This can be used if you need to install
           build tools in /usr during the build. This is stored in the
           usr subdirectory of the app dir, but will not be part of the
           final app.
       --tag=TAG
           Add a tag to the metadata file. This option can be used
           multiple times.
       --sdk-extension=EXTENSION
           When using --writable-sdk, in addition to the sdk, also
           install the specified extension. This option can be used
           multiple times.
       --extension=NAME=VARIABLE[=VALUE]
           Add extension point info.
       --sdk-dir
           Specify a custom subdirectory to use instead of usr for
           --writable-sdk.
       --update
           Re-initialize the sdk and var, don't fail if already
           initialized.
       --base=APP
           Initialize the application with files from another specified
           application.
       --base-version=VERSION
           Specify the version to use for --base. If not specified, will
           default to "master".
       --base-extension=EXTENSION
           When using --base, also install the specified extension from
           the app. This option can be used multiple times.
       --type=TYPE
           This can be used to build different types of things. The
           default is "app" which is a regular app, but "runtime"
           creates a runtime based on an existing runtime, and
           "extension" creates an extension for an app or runtime.
       --extension-tag=EXTENSION_TAG
           If building an extension, the tag to use when searching for
           the mount point of the extension.
       --verbose
           Print debug information during command processing.
       --ostree-verbose
           Print OSTree debug information during command processing.