After installing dev-embedded/arduino-1.0.5 you are instructed to run crossdev -s4 avr.

Unfortunately, sys-devel/crossdev-20140917 doesn't work on funtoo (FL-821, FL-1703), and in effect your freshly installed arduino IDE is useless.

Until the crossdev issues are resolved, it might be worth masking any packages depending on it, to make it clear that these packages will not work.

I'm setting this as a minor, as it's not a big issue. Once you realise the cause of the problem, it's easy enough to download binaries of arduino, with the requisit compilers.