Bug report

Bug description:

While inspecting the code for finding the causes of the issues of my build for CYGWIN, I found this piece of code:

CYGWIN supports /dev/fd and not /dev/self/fd as you can see here:

so a tiny fix is needed for adding __CYGWIN__ to the list of platforms to support the rigth entry with the set of file descriptors open in a process.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Windows

Linked PRs

• gh-148575: Use the right entry to read the set of file descriptors on CYGWIN #148576