When building ebuilds, portage sets the PKG_CONFIG_PATH environment variable. However, this value does not incorporate ${EPREFIX}, leading to problems on prefix systems. Reproducible: Always
Created attachment 359092 [details, diff] Proposed patch.
oh, yuck, that's necessary indeed!
This is fixed in git: http://git.overlays.gentoo.org/gitweb/?p=proj/portage.git;a=commit;h=68034f61f3da0aff4fca4b764620abd2c87c16c6
This is fixed in 2.2.7.