implement SailfishOS support, made in collaboration with vakkov

sorry for building your hopes up, it currently segfaults:
https://bpaste.net/show/319c346897f6
i hope someone can help me out there

i've continued what vakkov started with cleanups and i tried to make it so that other platforms still work (but i cannot test all of them :()
This should be `.PHONY: rpm` most likely. (`install_sailfish` is probaby also a phony target, see https://www.gnu.org/software/make/manual/html_node/Phony-Targets.html)