Make the edition, version, and hash easier to override to support
users who have a license for an older version of Softmaker Office.
With this change one can e.g. use Softmaker Office 2018 with:
softmaker-office.override {
officeVersion = {
edition = "2018";
version = "976";
sha256 = "0j6zm0cbxrcgm7glk84hvvbp4z0ys6v8bkwwhl5r7dbphyi72fw8";
};
}
This also helps people fix things when upstream has replaced the
previous version's tarball and this hasn't been fixed in nixpkgs yet.
