feat(docker): make containers multi-arch

I hope this will make the containers multi-arch

TODO:

There is a lot to comprehend, so here are some notes as to why:

u-root and linux are OK to build the "normal way", however with edk2 and coreboot I get errors when trying to compile to tool-chains - I suspect the problem to be native emulation not supporting all of the instructions required
- building x86 on x86 machine and arm64 on arm64 works fine, but building arm64 on x86 machine is broken
this means that I cannot build edk2 or coreboot multi-arch container on single x86 machine as I can u-root or linux
I looked into cross-compilation - aka cross-compile the cross-compilation tool-chains ... well that did not go well
one way would be to build each arch-container separately (x86 part on x86 machine and arm64 part on arm64 machine), publish them separately and then publish hand-crafted manifest connecting them together ... (see The hard way with docker manifest in Multi-arch build and images, the simple way
but we can avoid all of that with simply compiling the tool-chains separately on their respective machines and then just copy files into single multi-arch container (which can be done without any problems with simple native emulation)
so this is one step towards that
one advantage is that this way we can cache the compiled tool-chains for coreboot and speed up the build by one order of magnitude (normally they take around 1 hour to compile)

The final PR in the multi-arch saga

9elements / firmware-action