release.sh: allow REPO and GITBRANCH env override
release.sh: allow REPO and GITBRANCH env override

patch by Antoine Leca

Change-Id: Iabcf1189d8b5250536bb17e650f48f0e73fcde2c

veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi