Change build-testing-package.sh not to have optional arguments.

* Remove all dependencies installation in common evironment variables script
  (WTF)
* Remove scripts/build-testing-package.sh's arguments, as they are already
  available in travis. If they were supposed to be used by a human, then we
  should provide a *standard* way for it, like a Makefile shit, and not random
  (and wrong) bash scripts.