This ebuild (and ~arch mono-3.0.7's ebuild too) contain hardcoded dependency on paxctl and it run paxctl on './mono/mini/mono' in the middle of compile process. This works ok on kernels with PT_PAX, but fails on XATTR_PAX. I think either paxctl should be replaced with paxctl-ng, or there should be a way to use paxmark function from eclass.
mono-3.* uses paxctl-ng. This should work now.
(In reply to Anthony Basile from comment #1) > mono-3.* uses paxctl-ng. This should work now. Actually this is good enough, but I should add that using paxmark.sh does give more rebustness. It follows the same wrapper logic as pax-utils.eclass, falling back on other utilities should paxctl-ng not be found.