You receive this bug because this package does not respect my system's CC ( x86_64-pc-linux-gnu-gcc - /usr/bin/x86_64-pc-linux-gnu-gcc ) and calls directly gcc -/usr/bin/gcc The possible solutions to fix this issue are: 1)Fix the buildsystem, if you can 2)inherit toolchain-funcs and use tc-export CC 3)inherit toolchain-funcs and use emake CC="$(tc-getCC)" example: gcc -march=native -O2 -g0 -pipe -I. -I../Include -DTRACE_UNTESTED -DSPICE_3f -DPREDICTOR -DAN_pz -DAN_disto -DAN_noise -DHAS_STDLIB -fPIC -c cccssset.c g++ -march=native -O2 -pipe -I. -I../Include -DTRACE_UNTESTED -DSPICE_3f -DPREDICTOR -DAN_pz -DAN_disto -DAN_noise -DHAS_STDLIB -fPIC -I/var/tmp/portage/sci-electronics/gnucap-0.35.20091207/work/gnucap-2009-12-07/src -Wall -Wextra -c /var/tmp/portage/sci-electronics/gnucap-0.35.20091207/work/gnucap-2009-12-07/src/spice-wrapper.cc
+ 18 Jan 2013; Justin Lecher <jlec@gentoo.org> -gnucap-0.35.ebuild, + gnucap-0.35.20091207.ebuild: + Drop old; repect CC and CXX, #452838 +