Fix the following build failure with glibc >= 2.34 raised because closefrom doesn't return an int but a void since its addition with https://github.com/bminor/glibc/commit/607449506f197cc9514408908f41f22537a47a8c
posix-io.c: In function '_gpgme_io_spawn': posix-io.c:577:23: error: void value not ignored as it ought to be 577 | while ((i = closefrom (fd)) && errno == EINTR) | ^