[illwieckz]

Append the architecture name to loader binaries, implement box64 fallback, detect armhf multiarch support.

First commit of:

• Rebasing slipher's work on my CMake and VirtualMachine code #2018

Deep rewrite of VirtualMachine making possible to have multiple loaders per engine (especially for armhf/amd64+box64 on arm64). There was already some code for the windows amd64 loader on i686 engine, but this code makes it possible to do it for other platforms from the ground up, and does it for box64.

In the same way, the CMake code is genericized as well, loader files use explicit extensions in all cases so it's trivial to have multiple loaders.

This also implements the armhf support detection, and automatically fallbacks on box64 when not supported.

This also bring little changes that are not anymore useful, like some rework of the multiarch loader which is already expected to disappear in next commits, but keeping that change unmodified reduces future merge conflicts from future commits to merge. I strongly prefer to keep it that way.

After that one, only two commits will have to be merged and we will be ready to merge @slipher's change.

I already verified that all commits from #2018 are building complete releases each. I don't want to break that and I prefer to avoid redoing hour long testing by not inserting random purity changes between this and the next commits.

[illwieckz]

Merged as part of:

• Rebasing slipher's work on my CMake and VirtualMachine code #2018