This disables some kind of gawk useful output on segfault.
I haven't found an easy way of getting gawk use a newer libsigsegv with that
problem fixed.
So I do like the fedora people: disable libsigsegv.
(I don't know why this did not happen in the hydra machine. I could not build
gawk)
svn path=/nixpkgs/branches/stdenv-updates/; revision=19070