posix_spawn facility

[Bruno Haible]

I wrote:
>   * posix_spawn_file_actions_addfchdir_np
>     implemented in glibc, musl libc

Correction: posix_spawn_file_actions_addfchdir_np is implemented in
glibc, musl libc, FreeBSD ≥ 13.1, macOS ≥ 10.15.

Bruno