Massaging the build process

Preparing ground for further work on build scripts.
I'd appraise the "common wisdom" as generally saying that outside of `.sh` (which some legacy GNU-linux configurations still coerce into POSIX shell language) the shebang identifies the language to the shell and so extensions are unnecessary.

Nonetheless I'd certainly prefer `.bash` to `.sh`, if you find that acceptable. The worst that could be said about it would be that it is not the common practice; but there's nothing technically wrong with it either.