The keep_dir option was added but not used, and the "APKBUILD" suffix
was also forgotten in the commit that changed the script last.
Fixes 5d8cf85911
Signed-off-by: Pablo Correa Gómez <pabloyoyoista@postmarketos.org>
Part-of: <https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/9373>