add ubuntu focal to deb packaging workflow (#433)

Adds ubuntu focal to deb packaging workflow, this package will work
as long as the kernel is new enough.

Add kernel version to deb control file and drop the build for focal
on arm64.

.github/workflows/package-deb.yml

@@ -57,6 +57,8 @@ jobs:
           - { distro: debian, release: bookworm, arch: arm64 }
 
           # ubuntu kernels supported from 20.10 and up
+          # Rezolus will work on focal if a modern kernel is installed
+          - { distro: ubuntu, release: focal, arch: x86_64 } # 20.04
           - { distro: ubuntu, release: jammy, arch: x86_64 } # 22.04
           - { distro: ubuntu, release: jammy, arch: arm64 } # 22.04
           - { distro: ubuntu, release: noble, arch: x86_64 } # 24.04

debian/control

@@ -3,6 +3,7 @@ Section: devel
 Priority: optional
 Maintainer: IOP Systems <[email protected]>
 Standards-Version: 4.6.2
+Kernel-Version: 5.5
 Build-Depends: 
     debhelper (>= 10),
     pkg-config,