Implement single platform, cross-compiling, multiple distribution building.

[capn-freako]

With the release of version 4.1.0, we've brought the conda-build infrastructure up to date with current best practices, by using the Jinja templating mechanisms:

• {{ compiler(...) }} and
• {{ cdt(...) }}.

We should be now able to implement the cross-compiling necessary to implement single platform multiple distributions building.

==> Try to demonstrate multiple distributions building from a single platform.

Please, update the table below with your name and "X"s as appropriate, as you make progress.
That should facilitate better routing of queries for help with a particular combination of build/host platforms.

Developer	Build Platform	win-64	linux-64	osx-64	osx-arm64
David Banas	osx-arm64

[capn-freako]

==> On hold until someone researches cross-compiler generation and assess its ROI.

The conda-build infrastructure just allows for setting up the proper matrix of cross-compiled builds.
It does not provide the actual cross-compilers.
So, we'll need to get those, or build them ourselves, in order to proceed.
And this needs to be researched a bit and vetted for sufficient ROI.