There's something funky with your libdrm port, then. Over here, make install clearly shows:
Code:
install -o root -g wheel -m 444 intel_bufmgr.h '/usr/local/include'
test -z "/usr/local/libdata/pkgconfig" || .././install-sh -c -d "/usr/local/libdata/pkgconfig"
install -o root -g wheel -m 444 libdrm_intel.pc '/usr/local/libdata/pkgconfig'
Maybe something else in your /etc/make.conf is causing problems?
Adam