libarchive: *permanently* fix patch source and hash

Unfortunately github's *.patch URIs contain version of git generating them,
which changes from time to time. It seems that *.diff doesn't suffer from that.

(cherry picked from commit c814dab2eeb97c15f4a309e69435988fc3e65c6a)

Conflicts:
	pkgs/development/libraries/libarchive/default.nix