- this speeds up the old SKIP_TESTS targets build-nocheck and
  dev-install-nocheck
- this allows e.g. tinderboxes, which know that they just completed a
  build, to only read the files for the tests (and exclude the build
  itself)
- since the dep file can be quite large this might help performance in
  such scenarios quite a bit
- also moving this to extensions as it is merely a performance
  optimization

Conflicts:
	Makefile.in
	solenv/gbuild/Module.mk

Change-Id: I1265dbacdd9f3731fe755a1b997c2fa5ac1f7421
Reviewed-on: https://gerrit.libreoffice.org/2742Reviewed-by: Matúš Kukan <matus.kukan@gmail.com>
Reviewed-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>
Tested-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>