Passing arguments to the PEP517 sipbuild.api backend

[Michał Górny]

Hello,

I'm one of the maintainers of Python packages in Gentoo.  Lately we've
been working on transitioning from the legacy "setup.py install"
workflow to PEP517 build backends.  As part of that, I'd like to work
on switching the packages relying on sip -- starting with recently
released update to python-poppler-qt5 but eventually including PyQt.

Unfortunately, I can't find a way to pass options to the PEP517 backend
in the way that it is possible to the sip-build executable.  Is it
possible to inject options currently?  If not, could you please add such
a possibility?  The config_settings dictionary of build_wheel() method
seems to be the usual method of doing that (cf. setuptools accepting
{"--global_option": [...]}, though admittedly that double-dash is weird
there).

TIA.

-- 
Best regards,
Michał Górny