To install the AVR cross compiler toolchain, try: crossdev -t AVR
Of course you may need to "emerge crossdev
" first ;-)
There have been some problems reported with crossdev. Have a look to build scripts for Linux provided by the AVR-Freaks. This script has problems with the bfd-libs but the rest builds easily.
No ebuild for simulavr exists yet, but for me, the standard ./configure && make works. Let me know if this is not the case for you.