Feature request for envvar to disable using libyaml

[ilovezfs]

It would be great if there were an environment variable to disable using libyaml even if it's detected as available because passing --without-libyaml to pip can be non-trivial.

Currently, some packages in Homebrew routinely end up opportunistically linked to libyaml because they happen to use PyYAML and some other package in the same CI job has already installed libyaml, which PyYAML then uses even though the package using PyYAML doesn't itself depend on libyaml.

[ingydotnet]

Something like PYYAML_BUILD_WITHOUT_LIBYAML=1 seems reasonable.

[darkvertex]

For anyone wondering like I was, to pass the flag to pip it's via --install-option, ie:

python3 -m pip install PyYAML --install-option="--without-libyaml"