build: specify source tree in include/ for prerequisite
When doing an out-of-tree build, and thus setting VPATH,
GNU Make 3.81 on Ubuntu Trusty complains about Circular dependency of
include/Makefile and include/xlat.lst and drop them. The build fails
later due to headers malformed.
This might be due to bug #13529
"Incorrect circular dependancy"
https://savannah.gnu.org/bugs/?13529
which was fixed in 3.82.
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>