Add env for branch to use

aux/pull-n-build.sh

@@ -17,7 +17,11 @@ set -e -v
 		# repo URL set
 		if [ ! -d /repo ]; then
 			# repo needs to be cloned
-			git clone --recurse-submodules $REPO_URL /repo
+			# check if there is a specific branch to clone
+			if [ ! "$REPO_BRANCH" == "" ]; then
+				BRANCHCMD="--branch $REPO_BRANCH"
+			fi
+			git clone --recurse-submodules $BRANCHCMD $REPO_URL /repo
 		else
 			# no - pull existing repo
 			cd /repo && git pull --recurse-submodules