mklive: multiple improvements and fixes.

- Does not need bash anymore, a POSIX shell is enough.
- Avoid installing base-system twice to generate the initramfs.
- Reconfigure some pkgs in the rootfs... otherwise some system users won't be created.
- Added -K opt to not remove builddir.

README.md

@@ -11,7 +11,6 @@ This repository contains utilities for Void Linux:
 #### Dependencies
 
  * xbps>=0.35
- * GNU bash
  * parted (for mkimage)
  * qemu-user-static binaries (for mkrootfs)