secubox-dpi and secubox-toolbox-ng are CGO_ENABLED=0, GOARCH=arm64,
-mod=vendor offline cross-compiles. They failed the arm64 build only
because golang-go was never installed, so dpkg-checkbuilddeps aborted on
their `Build-Depends: golang-go (>= 1.22)`. Not a CGO cross-toolchain
gap. ubuntu-24.04 ships golang-go >= 1.22; installing it lets the pure-Go
arm64 cross-compile run on the amd64 runner.
Unblocks a complete amd64+arm64 package set for the apt repo + arm64 images.