Backport patch fixing stdlib detection

[h-vetinari]

Backport for conda/conda-build#5195 to unblock the very long-running migration that's going to be necessary for adding this to all our recipes.

I've asked if conda-build would consider backporting the PR to 24.1.x, which would be even better. In either case, I think a backport makes sense w.r.t. the urgency (e.g. promised switch to cos7 in June or macOS 10.13 woes like being unable to release current libcxx) resp. how long I expect it to take to add {{ stdlib("c") }} across all our recipes.

[conda-forge-webservices]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[h-vetinari]

@conda-forge/conda-build @mbargull

Could you let me know your thoughts about this PR? (or for the Anaconda folks, backporting conda/conda-build#5195 to 24.1.x upstream directly).

It would be very helpful for unblocking the stdlib migration work.

[h-vetinari]

Now that #221 was merged, this is obsolete, closing