xorg-server.m4: just all cflags instead of just sdkdir
Instead of fetching just the sdkdir variable of xorg-server using pkg-config, simply get all of the CFLAGS. Aside from completeness, this helps builds in sysroots as pkg-config knows what to do with --cflags but doesn't remap arbitrary variables.
Signed-off-by: Ross Burton ross.burton@intel.com