Add indirect dependencies that cmake complains about and remove ccache
because it currently fails to build on NixOS unstable.
Signed-off-by: Rafael Kitover <rkitover@gmail.com>
Add a `default.nix` with the list of dependencies.
Detect NixOS in installdeps and display the `nix-shell` command to
build.
Signed-off-by: Rafael Kitover <rkitover@gmail.com>