Add Arm build

[gbraad]

Building on multiple runners is possible

  runs-on: ubuntu-24.04-arm

but perhaps the simplest approach is to first try:

podman build --platform linux/amd64,linux/arm64/v8 ...

[gbraad]

The build finishes and tags for amd64, but fails for arm:

--> 0bedfe82aeb9
Successfully tagged localhost/test:latest
0bedfe82aeb9e0f4e156233e0566ddc8847e3946b26df16a8a3a24ed0805c5d7
Error: [linux/arm64/v8]: building at STEP "RUN chmod 640 /etc/shadow": while running runtime: exit status 1

Details:

[linux/arm64/v8] STEP 1/15: FROM quay.io/fedora/fedora:41
Trying to pull quay.io/fedora/fedora:41...
Getting image source signatures
Copying blob 46d6d6fb8c71 done   | 
Copying config 7ecd7e5f1a done   | 
Writing manifest to image destination
[linux/arm64/v8] STEP 2/15: LABEL org.opencontainers.image.source = "https://github.com/gbraad-devenv/fedora"
--> b846bcfbc177
[linux/arm64/v8] STEP 3/15: USER root
--> 9dde3d68749c
[linux/arm64/v8] STEP 4/15: RUN chmod 640 /etc/shadow
exec container process `/bin/sh`: Exec format error
[linux/amd64] STEP 1/15: FROM quay.io/fedora/fedora:41
Trying to pull quay.io/fedora/fedora:41...
Getting image source signatures
Copying blob 0a0860669fc2 done   | 
Copying config 1d17320df1 done   | 
Writing manifest to image destination
[linux/amd64] STEP 2/15: LABEL org.opencontainers.image.source = "https://github.com/gbraad-devenv/fedora"
--> b1fb74236bb9
[linux/amd64] STEP 3/15: USER root
--> 523151c13a75
[linux/amd64] STEP 4/15: RUN chmod 640 /etc/shadow

Step 4 is the first RUN-command and it errors with: exec container process /bin/sh: Exec format error

[gbraad]

Dotfiles builds without issues