You need to have exiv2 with BMFF support installed on your machine, this means using the one from your distro or compiling it yourself. Needs at least 0.27.4.
You need to clone darktable source including the submodules and replace the rawspeed submodule with the one from here: GitHub - cytrinox/rawspeed at canon_cr3
Afterwards just compile darktable as you normally would and it should be fine