Set Bash explicitly as default shell in Makefile

[phansys]

GNU make uses /bin/sh by default if the SHELL variable is not set to a different value (see Choosing the Shell).

In my environment (and in many of my previous bashism incursions), I found myself fighting with syntax issues derived from the fact that [ x == y ] does not work with sh:

/bin/sh: 1: [: unexpected operator

See:

• https://unix.stackexchange.com/a/72042
• https://stackoverflow.com/a/18102991

BTW, I've opted to set /bin/bash as the default shell instead of changing the script syntax to make it compatible with /bin/sh, because the shebangs at the bin/ directory are already using /bin/bash.

[greg0ire]

Thanks @phansys !