[Compat][Emerge][Gentoo] emerge missing /dev/fd

```sh
# Fix missing /dev/fd
[ -d /proc/self/fd ] && [ ! -e /dev/fd ] && ln -s /proc/self/fd /dev/fd
[ -L /dev/fd/0 ] && [ ! -e /dev/stdin ] && ln -s /dev/fd/0 /dev/stdin
[ -L /dev/fd/1 ] && [ ! -e /dev/stdout ] && ln -s /dev/fd/1 /dev/stdout
[ -L /dev/fd/2 ] && [ ! -e /dev/stderr ] && ln -s /dev/fd/2 /dev/stderr
```