Gentoo's Bugzilla –
Attachment 330064 Details for
Bug 439138x11-base/xorg-server-1.13 USE=minimal - In file included from ...work/xorg-server-1.13.0/hw/xfree86/os-support/linux/lnx_platform.c:7:0: /usr/include/xf86drm.h:40:17: fatal error: drm.h: No such file or directory