Created attachment 294701 [details, diff] ebuild.patch e.g. gcc -I. -I/tmp/portage/net-irc/ircii-20110228/work/ircii-20110228/include -I/tmp/portage/net-irc/ircii-20110228/work/ircii-20110228/source/rijndael -pipe -march=native -O2 -g0 -DHAVE_CONFIG_H -c /tmp/portage/net-irc/ircii-20110228/work/ircii-20110228/source/alias.c works for me that patch.
I decided to go with just `tc-export CC' in src_configure() instead of overriding CC at make. Thanks for the bug. The reason I couldn't reproduce it (see bug 392771 comment 2) was that I was using multilib-portage, which already assigns CC=$(tc-getCC). I was able to reproduce it with my gentoo-prefix installation.