flatpak (build_manifest): some fixes needed after runtime update: - removed `--optimize=1` for lxml, as it is making the build fail - added build flag on x86_64 for Pillow (will need to be adapted if we build on other architectures) - added a module for Python 2.7.16, Python 2 not being included anymore in the runtime - DEFAULT_MANIFEST modules are put at the beginning of modules

{
    "_build_settings": {
        "package": "sat",
        "wrapped_command": "jp",
        "dev_repos": {"type": "hg", "url": "https://repos.goffi.org/sat"},
        "icon": "https://repos.goffi.org/sat_media/raw-file/tip/icons_svg/sat.svg",
        "desktop_file": "org.salutatoi.Jp.desktop",
        "appdata_file": "_tpl_org.salutatoi.Jp.appdata.xml"
    }
}