When klibc is installed, configure wants to use klcc and compilation fails due to an inexistant command-line argument (-idirafter). Workaround for users : temporarily rename /usr/bin/klcc to avoid its detection. I already reported the bug to upstream.
fixed in cvs http://sources.gentoo.org/sys-block/nbd/nbd-2.9.8.ebuild?r1=1.4&r2=1.5 http://sources.gentoo.org/sys-block/nbd/nbd-2.9.10.ebuild?r1=1.1&r2=1.2