[pypy-issue] Issue #2808: crypt() not defined in unistd.h breaks build on Fedora 28 (pypy/pypy)

[pv]

New issue 2808: crypt() not defined in unistd.h breaks build on Fedora 28
https://bitbucket.org/pypy/pypy/issues/2808/crypt-not-defined-in-unistdh-breaks-build

pv:

Apparently Fedora (and probably also other systems) are using libxcrypt instead of glibc crypt(). This breaks pypy's crypt module build (translation fails with c compilation error), since crypt() is defined in crypt.h and no longer in unistd.h.

https://fedoraproject.org/wiki/Changes/Replace_glibc_libcrypt_with_libxcrypt

Not sure how pypy handles system-specific includes, probably just adding `includes=["crypt.h"]` is not the right thing on all systems.