possible incorrectness in libffi include dir assignment, doesn't seem impactful

This looks like an obvious mistake but I don't think it matters because the pkgconfig files are correct and provide the path ultimately:

https://github.com/codrsquad/portable-python/blob/89a620140f6f7bb066f77774c23187d78cf96275/src/portable_python/cpython.py#L142

            if self.active_module(LibFFI):
                yield f"LIBFFI_INCLUDEDIR={self.deps_lib}"

I'll refrain from opening a PR because I'm not sure... it's possible that this is necessary due to libffi nuances and just looks wrong, but there's no comment or commit message to indicate if thats the case.

Lisez src/portable_python/cpython.py à la ligne 142 et comparez l’affectation de LIBFFI_INCLUDEDIR avec les chemins libffi pkg-config mentionnés dans l’issue. Vérifiez si cette affectation affecte le build malgré des fichiers pkg-config corrects. Le travail est terminé lorsque le comportement est confirmé et que l’écart est documenté ou corrigé au moyen d’un test ciblé, si le dépôt en fournit un.