Update install_dev.sh

scripts/install_dev.sh

@@ -76,7 +76,9 @@ echo "use system version: ${OSNAME}"
 curl -fsSL https://raw.githubusercontent.com/midoks/mdserver-web/dev/scripts/install/${OSNAME}.sh | bash
 
 chmod +x /www/server/mdserver-web/mw-cli
-ln -s /www/server/mdserver-web/mw-cli /usr/bin/mw-cli
+if [ ! -e /usr/bin/mw-cli ]; then 
+	ln -s /www/server/mdserver-web/mw-cli /usr/bin/mw-cli
+fi
 
 endTime=`date +%s`
 ((outTime=(${endTime}-${startTime})/60))