cross/{gcc,musl,grub-efi-x86}: upgrade to latest versions

Oliver Smithrequested to merge
ollieparanoid/pmaports:upgrade-cross-pkgs into master

Upgrade all packages that currently cause the upstream compat check to fail.

GCC was upgraded with pmbootstrap!2521 (merged) (without removing makedepends="$makedepends_build $makedepends_host" for now as currently pmbootstrap doesn't support this yet - fixing this is part of the pmb MR).

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