This is the important message:
!!! All ebuilds that could satisfy "cross-avr/binutils" have been masked.
You can unmask one of the
cross-avr/binutils packages, but they are all marked as corrupting something. Basically this means that when you compile the package it will not work anyway. Not sure in what way things get corrupted. How to unmask packages in Gentoo is pretty well explained in the Gentoo handbooks, and otherwise help can be found on http://unix.stackexchange.com/https://unix.stackexchange.com/ It's been too long for me to remember from the top of my mind.