linux: replace the initramfs source during post_patch

[lrusak]

This makes it so we don't have any surprise options appearing or disappearing after the kernel has been unpacked.

Maintainers please update your configs:

• Amlogic @chewitt
• Rockchip @Kwiboo
• RPi/Generic @MilhouseVH
• Allwinner @jernejsk

aarch64 kernels may have initramfs compression (if the kernel is uncompressed)
arm kernels do not use initramfs compression (the entire kernel is compressed)

We should probably unify that at some point but it is outside of the scope of this PR.

I can either pick your commits and squash them in or you can push them directly to this branch (or you can PR to my branch).

Thanks.

[MilhouseVH]

@lrusak thanks for this. Please squash the RPi/Generic updates using f1ffbd7

There's another couple of "annoyances" when running make oldconfig that are capable of introducing build host specific changes:

# Compiler: gcc (Ubuntu 7.2.0-8ubuntu3.2) 7.2.0

and

CONFIG_GCC_VERSION=70200

Both of these changes should ideally be ignored when submitting a config change to avoid flip-flopping these options/comments whenever one developer submits a minor option change while using a different version of gcc to the previous config submitter. It's a cosmetic thing, but just adds potential noise to a config change and maybe something to bear in mind (as it's not specifically called out in the workflow notes).

[MilhouseVH]

Allwinner: f2665c2

Amlogic: 13175aa

Rockchip: 3ba8b26 (plus extras, @Kwiboo please double check)

[lrusak]

@MilhouseVH thanks. I've left the commits separate right now until I get a sign off from each maintainer 👍

[Kwiboo]

@MilhouseVH Rockchip changes looks good, I have the same changes after a make olddefconfig, thanks!

[MilhouseVH]

Ping @chewitt 😄

[chewitt]

fine with me, I'll make the changes (or adjust to whatever was merged) when I next update the current draft PR .. will be a while due to work and other real-life things.