vmlinuz.kpart is too small for google-x64cros (No space left on device)

Describe your issue

google-x64cors images don't build anymore in bpo since 20240704. These devices have a small cgpt/depthcharge partition, into which the kernel and initramfs get installed.

I'll disable building these images until this is fixed. It should be feasible to fix this, but if we can't, then we must move the device to the testing category before releasing v24.12.

How to reproduce your issue?

$ pmbootstrap config device google-x64cors
$ pmbootstrap config ui console
$ pmbootstrap config kernel edge
$ pmbootstrap install --password x

(019829) [14:13:08] (native) % dd if=/mnt/rootfs_google-x64cros/boot/vmlinuz.kpart of=/dev/installp1
dd: error writing '/dev/installp1': No space left on device

What device are you using?

google-x64cros

On what postmarketOS version did you encounter the issue?

• edge (master branch)

• v24.06

• I confirm that the issue still is present after running sudo apk upgrade -a

On what environment did you encounter the issue?

all

Additional information

Ideas for fixing this:

• heavily compress the initramfs, currently: 03:04:17.447630 Unknown or no compression format set, using gzip
  • please do before and after comparisons
  • try to use a compression that gives us the tiniest size, so we have some room in case the kernel/initramfs grow again
  • note that I've already set it to use the postmarketos-initramfs-minimal in !5269 (merged)
• can we increase the size of the partition?
• bonus points for making a pmbootstrap patch to output a more useful error message if the dd command fails. Instead of just "No space left on device" we could point to this issue.

Related discussion: !5376 (comment 2021300720)

Tagging maintainers: @JustSoup321 @alpernebbi @jenneron