For instance: CFLAGS="-march=native -O3" emerge -1 =app-arch/unar-1.6 [...] x86_64-pc-linux-gnu-gcc -std=gnu99 -march=native -O3 -O2 -Wno-import -Wno-multichar -g -D_FILE_OFFSET_BITS=64 -isystem /usr/include/GNUstep -DGNUSTEP -DGNU_RUNTIME=1 -D_NATIVE_OBJC_EXCEPTIONS -fgnu-runtime -fexceptions -fobjc-exceptions -fconstant-string-class=NSConstantString -MMD -MFBuild/XADTest2.d -MTBuild/XADTest2.o -c XADTest2.m -o Build/XADTest2.o [...]
should be fixed with 1.8.1