cross/grub-efi-x86: update and check version in CI
Two commits:
- cross/grub-efi-x86: update to 2.02-15
- CI: upstream compatibility: add grub-efi-x86
@nickre: FYI. grub-efi-x86 will be kept in sync with Alpine's package from now on
This is a trivial update. Merging as soon as CI goes through.
Related literature for admins: https://wiki.postmarketos.org/wiki/Repository_maintenance#Fixing_upstream_incompatibilities_with_Alpine.27s_repository