Preliminary nix expression for CI via Hydra/Nix

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Load package.el in Makefile.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Add native elisp dependencies.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Merge branch 'nix'

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>