Reduce binary size of kairos components

[mudler]

Is your feature request related to a problem? Please describe.
Currently UKI can suffer of hard limit on the EFI files meant to be booted. This is problematic as we hit systemd/systemd#25911 when trying to build big images.

Describe the solution you'd like
In order to optimize the size of the images, we should try to reduce the image size of the golang binaries we bundle in the image, for instance:

• kairos-agent
  • Reduce doc sizes to make kairos-agent smaller kairos-docs#151
• immucore
• kcrypt
• kcrypt-challenger
• luet
• provider-kairos
• edgevpn
• ...

Also, similarly we can try to compress the k3s binary as well.

Describe alternatives you've considered
N/A

Additional context
This is partially related to #2283, but that story is just about the ubuntu base image dependencies.

To strip binaries, we need to change how we build/package them in kairos-io/packages.

Build phase:

During build, we can specify the -w and -s build flags that strip part of the debug symbols, for instance:

go build -ldflags "-w -s"

For compressing I suggest to use upx right after build. For example:

upx -1 <binary> 

[mauromorales]

⚠️ immucore still hasn't been compressed

before:

...
9920    /usr/bin/kcrypt
15872   /usr/bin/immucore
23168   /usr/bin/nerdctl
23432   /usr/bin/snap
26220   /usr/bin/luet
31424   /usr/bin/edgevpn
43012   /usr/bin/kube-vip
47044   /usr/bin/kubectl
54468   /usr/bin/k3s
89924   /usr/bin/k9s
93956   /usr/bin/kairos-agent
519300  total

After:

...
5096    /usr/bin/kcrypt
11592   /usr/bin/nerdctl
11880   /usr/bin/kairos-agent
14580   /usr/bin/edgevpn
16704   /usr/bin/immucore
16848   /usr/bin/snap
19340   /usr/bin/kubectl
25748   /usr/bin/k9s
27368   /usr/bin/luet
44312   /usr/bin/kube-vip
56504   /usr/bin/k3s
296316  total

[mauromorales]

final standard efi file size:

kairos@localhost:~$ ls -lash /efi/EFI/kairos/
total 2.7G
8.0K drwxr-xr-x 2 root root 8.0K Feb 27 08:33 .
8.0K drwxr-xr-x 5 root root 8.0K Feb 27 08:22 ..
912M -rwxr-xr-x 1 root root 912M Feb 27 08:33 active.efi
912M -rwxr-xr-x 1 root root 912M Feb 27 08:33 passive.efi
912M -rwxr-xr-x 1 root root 912M Feb 27 08:33 recovery.efi

[jimmykarily]

We are done reducing sizes. Closing.