Force MacOS SDK version to "10.11"

This is due to the fact that the new CI machines are on 10.14

Signed-off-by: Ulysses Souza <ulyssessouza@gmail.com>

Release.Jenkinsfile

@@ -72,6 +72,9 @@ pipeline {
                     agent {
                         label 'mac-python'
                     }
+                    environment {
+                        DEPLOYMENT_TARGET="10.11"
+                    }
                     steps {
                         checkout scm
                         sh './script/setup/osx'