Use '/usr/bin/env bash' instead of hardcoding '/bin/bash'.

This makes the scripts more portable by not making assumptions about
the location of the bash shell. `env' will search for bash in PATH.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Don't use /usr/bin/env bash in Makefile.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Merge pull request #746 from the-kenny/fix-bash

Use 'bash' instead of hardcoding '/bin/bash'.