`ls --ignore` behaves differently

[ackerleytng]

Discovered while working on https://github.com/uutils/coreutils/issues/3628

$ ls
a  b  c  d  e
$ ~/projects/coreutils/target/debug/coreutils ls
a  b  c  d  e
$ ls --ignore '[a]'
b  c  d  e
$ ~/projects/coreutils/target/debug/coreutils ls --ignore '[a]'
b  c  d  e
$ ls --ignore '[!a]'
a
$ ls --ignore '[^a]'
a
$ ~/projects/coreutils/target/debug/coreutils ls --ignore '[!a]'
a
$ ~/projects/coreutils/target/debug/coreutils ls --ignore '[^a]'
b  c  d  e
$

I'll work on this!