Set the default shell used in Makefile to bash
Set the default shell used in Makefile to bash

The default shell in Makefile is `sh` and since bashisms are used in the
Makefile, some of the targets fail, depending on setting of the system
(not an issue on vanilla Fedora where `/bin/sh` is a symlink to `bash`).

leapp-to/prototype,leapp-to/prototype,leapp-to/prototype,leapp-to/prototype