Add pdm-backend, the build backend used by PDM that supports latest
packaging standards. Version 2.1.7 provides:
- Rename tag-pattern to tag_regex in the docs
- Copytree handle existing dirs
- Normalize the dist info name in the wheel
Signed-off-by: Leon Anavi <leon.anavi@konsulko.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
