Fixing Makefile for proper Optiboot build
Fixing Makefile for proper Optiboot build

Signed-off-by: Thibaut VIARD <fc50013fb781c145d1d7c1536a9be55351d6f2b7@sam-geek.org>

AtmelUniversityFrance/atmel-avr-xmini-boardmanagermodule,AtmelUniversityFrance/atmel-avr-xmini-boardmanagermodule