mingw32-git: Fix removing the copied Git Perl modules

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
mingw32-git: Print more post-install progress info

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
mingw32-git: Fix post-install action when running from installer under cmd.exe

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>