New review comment by ericonr on void-packages repository

https://github.com/void-linux/void-packages/pull/27327#discussion_r546856857

Comment:
If you want to upstream this (please do :) ), just tell upstream that it's completely unnecessary. This is a glibc internal file, you are never supposed to touch it yourself.

They should just define something like `#define _XOPEN_SOURCE 500` at the top of their file, if it doesn't build now.