main/postmarketos-mkinitfs: add workaround for x86_64 qemu on aarch64 (MR 5653)

This adds a workaround for:
https://gitlab.com/qemu-project/qemu/-/issues/2560

The tl;dr is that there's a qemu bug that prevents running mkinitfs (or
any go apps) on a aarch64 host using qemu-x86_64. I've basically been
unable to build x86_64 images on my aarch64 system for months now, which
is less than ideal :(

Patch is in mkinitfs 2.6.1, but picked to the older version in master until !5636 is merged

[ci:skip-build]: already built successfully in CI