utils/getdeveloperlib.py: force foward-slash for pattern matching
Force relative file path resolution of DEVELOPERS file entries to use
forward-slash separators since pattern matching assumes forward slashes.
This is to help permit uses invoking `get-developers` on Platforms where
`os.sep` may not be a forward slash.
Signed-off-by: James Knight <james.d.knight@live.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>