u-boot: add option to build specific revision

u-boot/tools/build

@@ -6,7 +6,7 @@
 TARGET_ARCH=$1
 
 if [ ! -n "$TARGET_ARCH" ]; then
-	echo "Usage: $0 <arch> [board]"
+	echo "Usage: $0 <arch> [board|all] [commit]"
 	exit 1
 fi
 
@@ -52,13 +52,17 @@ GIT_REPO="git://git.denx.de/u-boot.git"
 
 echo "Cloning sources..."
 git clone $GIT_REPO $TMP
+if [ $# -eq 3 ]; then
+	git -C $TMP checkout $3
+fi
 
 GIT_DATE=$(git -C $TMP log -1 --format=%cd)
 GIT_HASH=$(git -C $TMP log -1 --format=%H)
 
-WORK_QUEUE=$(find $TARGET_ARCH/ -mindepth 1 -type d)
-if [ $# -eq 2 ]; then
+if [ $# -ge 2 -a "$2" != all ]; then
 	WORK_QUEUE="$TARGET_ARCH/$2"
+else
+	WORK_QUEUE=$(find $TARGET_ARCH/ -mindepth 1 -type d)
 fi
 
 for dir in $WORK_QUEUE; do