flatpak: Drop useless build options
They are already defined in the runtime.
See https://github.com/flatpak/freedesktop-sdk-images/blob/1.6/org.freedesktop.Sdk.json.in#L110.
They are already defined in the runtime.
See https://github.com/flatpak/freedesktop-sdk-images/blob/1.6/org.freedesktop.Sdk.json.in#L110.