conda-build replacement

[analog-cbarber]

Add a new conda-build subcommand that acts as a drop-in replacement for the real conda-build
for suitable pure-python recipes.

This would:

1. Process the jinja templates
2. Copy the sources into a build tree like conda-build does
3. Would change the pip install command to pip wheel to build the wheel
4. Use whl2conda build to build the package
5. If there is a test section, would use whl2conda install to build the environment
6. Would run the tests
7. If everything is fine, would use whl2conda install --conda-bld to put in build directory

There should be additional options to use whl2conda dependency renames instead of
the conda recipe dependencies.

[analog-cbarber]

We could add options to the subcommands to use information from a
conda-build recipe and also add a test subcommand and implement
the build from those parts.

[analog-cbarber]

Should display elapsed time at the end.

[analog-cbarber]

Conda build repo is at: https://github.com/conda/conda-build

[analog-cbarber]

The jinja templates and environment markers in the meta.yaml file can be rendered using
the conda_build render api: (source)

from conda_build import api
md, needs_download, needs_rerender = api.render(recipe_path)

Conda build depends on conda, so it can only be installed in the base environment, so this would have to
be run in a base environment subprocess and the rendered recipe saved in JSON or yaml format.

[analog-cbarber]

There appears to be a conda render subcommand that is part of conda-build, so we should just use that.

[analog-cbarber]

It appears that conda render copies the sources into conda-bld/<project-name>_<timestamp>/work and leaves it there.

[analog-cbarber]

A basic version of this feature is on main (perhaps I should have left it on a branch).

I should add tickets for remaining issues to make production ready.

[analog-cbarber]

The initial prototype has been done, so I am going to close this.

There will be other issues and a milestone track the production-ready feature.