Make it possible to declare an archful package (#10)

[befeleme]

cc: @hroncok This works on tornado which requires gcc - the package is successfully build when spec file is generated from the attached config file. The fact that a package is archful still needs to be explicitly declared by the packager either by using CLI option or by manually adding the option to config file. It's not perfect, but it enables getting the repeatable results for the same config.

Nevertheless, I'd like to start building understanding what we can and cannot detect from working with the sources/building them wrt extension modules. As my knowledge of the domain is scarce, would you be up to a demonstration on an example?

[hroncok]

As my knowledge of the domain is scarce, would you be up to a demonstration on an example?

Sure. Let me know tmrw.

What I know:

• when you actually install a package with extension module(s), it installs to %python3_sitearch (platlib in sysconfig terms) instead of %python3_sitelib (purelib in sysconfig terms)
• built/installed packages with extension modules usually have .so files, albeit I have seen the archfulness forced
• the generated dist-info metadata (using prepare_metadata_for_build_wheel) does not indicate archfulness in any way

[befeleme]

Merged in c78ed80705d8b64317634c2cd8e14e5d1a4fbdae.