ci: Improve the script to kill processes a bit

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
ci: Turn install-here into a cmd to be able to run it without a shell

This allows the installer so run rebaseall as a post-install step on the
CI server.

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
installer: Do not skip rebasing DLLs anymore in silent mode

This is not necessary anymore as install-here.cmd does not spawn a shell.

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