Yes, there is something wrong.
On Ubuntu Mir is using /usr/include/drm/drm.h, (installed by linux-libc-dev).
Mir's CMakeLists.txt picks up /usr/include/libdrm/ (which contains an identical drm.h installed by libdrm-dev)
It looks as though we should be using <drm.h> from libdrm-dev, not <drm/drm.h>
Yes, there is something wrong.
On Ubuntu Mir is using /usr/include/ drm/drm. h, (installed by linux-libc-dev).
Mir's CMakeLists.txt picks up /usr/include/ libdrm/ (which contains an identical drm.h installed by libdrm-dev)
It looks as though we should be using <drm.h> from libdrm-dev, not <drm/drm.h>