Travis: Fix failing macOS build job
See also:
@@ -177,6 +177,7 @@ matrix:
- swig
- yajl
- zeromq
+ update: true
env:
# Unfortunately the tests for the Xerces plugin fail: https://travis-ci.org/ElektraInitiative/libelektra/jobs/483331657#L3740
- PLUGINS='ALL;-xerces'
