[ci] Set SSL_CERT_FILE variable for mac to point to the CA bundle

in order for davix to be able to read https

Author: dpiparo

.github/workflows/root-ci.yml

@@ -84,6 +84,9 @@ jobs:
         (github.repository_owner == 'root-project' && github.event_name != 'pull_request') ||
         (github.event_name == 'pull_request' && !(contains(github.event.pull_request.title, '[skip-ci]') || contains(github.event.pull_request.title, '[skip ci]')))
 
+    env:
+      SSL_CERT_FILE: ${{ secrets.SSL_CERT_FILE_VALUE }} # necessary for davix to connect to https
+
     permissions:
       contents: read