I haven’t used it myself, but apparently Singularity helps get around some of these cross-linux dependency issues. It’s apparently able to be used with Slicer. Probably still requires some help from the cluster sysadmins if you want to install it.
But getting back to the build error, I’m not sure why qMRMLWidgetsCxxTests would be built if testing is turned off. In any case the Slicer app code should not depend on it, so maybe you can do make -k to build everything and just ignore the failing build of the test (or maybe you’ll get a similar link error on the app level - this looks like a qt issue - you might also try turning off Slicer_BUILD_WEBENGINE_SUPPORT).