[][openwrt][common][build][Fix autobuild fail]

[Description]
Fix autobuild flow fail due to 21.02 feed config updated

[Release-log]
N/A

Change-Id: Idd05a90dbdb01b520dcea518b4335cb775ef0957
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6439609
diff --git a/prepare_sdk.sh b/prepare_sdk.sh
index ab555dc..4f94756 100755
--- a/prepare_sdk.sh
+++ b/prepare_sdk.sh
@@ -4,8 +4,16 @@
 
 if [ -f feeds.conf.default_ori ]; then
 	OPENWRT_VER=`cat ./feeds.conf.default_ori | grep "src-git packages" | awk -F ";openwrt" '{print $2}'`
+
+	if [ -z ${OPENWRT_VER} ]; then
+		OPENWRT_VER=`cat ./feeds.conf.default_ori | grep "src-git-full packages" | awk -F ";openwrt" '{print $2}'`
+	fi
 else
 	OPENWRT_VER=`cat ./feeds.conf.default | grep "src-git packages" | awk -F ";openwrt" '{print $2}'`
+
+	if [ -z ${OPENWRT_VER} ]; then
+		OPENWRT_VER=`cat ./feeds.conf.default | grep "src-git-full packages" | awk -F ";openwrt" '{print $2}'`
+	fi
 fi
 
 if [ -z ${1} ]; then