Validation queue needs to test multiple build configurations

[Chris Hillery]

At a minimum, we wish to test with ZORBA_WITH_BIG_INTEGER set both on and off.

More generally, we should support multiple build configurations, each with potentially different sets of tests run. For example, we don't necessarily need to run XQTS with every configuration.

[Chris Hillery (ceejatec)]

Probably the validation queue should NOT short-circuit - if one build configuration fails to build, it should still try the rest. That way we get the most information per queue run. Probably any egregious build failures will cause all configurations to fail quickly, so there isn't much time penalty.

[Chris Hillery (ceejatec)]

It will be necessary for each build+test configuration to submit results as separate CDash builds, and the passing/failing tests for each build should be linked from the validation queue's log.html.