This is not a backport. The upstream code does not have the change
that the patch introduces:
https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/src/gbm/main/backend.c
Please do a proper upstream submission, and do not tell untruths in
your submissions here. You do not want your future contribut
Commit introduces a patch that allows for gbm to
be built with an empty backend. There are situation
where mesa-gl is the preferred provider for virtual/libgbm,
virtual/libgl, virtual/mesa, etc... But the x11 DISTRO_FEATURE
isn't included this leads to build errors such as
| /../../../ld: src/gbm/
