Please add support for posix_spawn_file_actions_chdir and posix_spawn_file_actions_fchdir

[CameronNemo]

• POSIX.1-2024 includes these

• linux gnu, musl, bionic have implementations, using the _np suffix

• freebsd uses _np suffix, netbsd implements with no suffix AFAICT

• seems like macos implements with the _np suffix (but not necessarily iOS?)

• haiku does implement with _np suffix

• Not sure about other implementations that might exist. seems like openbsd does not implement it.

• posix docs

• gnu docs

• freebsd docs

• netbsd docs

• MacOS XNU spawn.h

• Haiku gnu-compat spawn.h