gfx-drm should support USERLAND_ARCHIVES
gfx-drm uses libdrm source archive. When archive is unavailable, there's no easy way to tell gfx-drm 'use cached archive', especially when it is wrapped in oi-userland build script, which does git clean -f before publishing.
In oi-userland we use USERLAND_ARCHIVES environment variable to point to the archive of pre-downloaded files. It would be good to use this variable in the same way for gfx-drm.