It's in POSIX-future and some applications have started depending on it.
It's easier to backport into musl than fix each individual package.
Since we are adding a new interface to libc, update common/shlibs entry
as well. This should probably have been done for all musl updates.
And since we are here, also backport:
- isascii fix (removes the need for a patch in fceux)
- make epoll a cancellation point (fixes a bug in jack pipewire utilities)
beb3f7fb1f