You receive this bug because this package does not respect my system's CFLAGS The possible solutions to fix this issue are: 1)Fix the buildsystem, if you can 2)inherit toolchain-funcs and use emake CFLAGS="${CFLAGS}" (if it does not break) There is only one line with unrespected cflags: x86_64-pc-linux-gnu-gcc -DHAVE_CONFIG_H -I. -I../src/include -I../src/include -I../src/include -c -o cpi.o cpi.c