Please bump avrdude to version 6.1. There hasn't been any announcement of the new version on the project website (I guess that's why you missed it), but it's available in their download/ directory. The bump is a simple copy-only one.
*avrdude-6.1 (24 Nov 2014) 24 Nov 2014; Yixun Lan <dlan@gentoo.org> +avrdude-6.1.ebuild: version bump, requested and tested by @perfinion