Let jenkins.sh build against a chosen wolfSSL branch

Author: aidangarske

mynewt/jenkins.sh

@@ -22,7 +22,7 @@ newt upgrade
 popd > /dev/null
 
 # deploy wolfssl source files to mynewt project
-git clone https://github.com/wolfSSL/wolfssl.git
+git clone ${WOLFSSL_REF:+--branch ${WOLFSSL_REF}} https://github.com/wolfSSL/wolfssl.git
 WOLFSSL=`pwd`/wolfssl
 ${WOLFSSL}/IDE/mynewt/setup.sh ${NEWTPROJ}