* Fix temporary directory prefix.
* Add test run for Google V8 benchmark; while it's pointless for performance
measurement when the test runs in the cloud, it still provides a useful
regression harness.
* Add qecmatest and apitest assert and valgrind variants.
* Add valgrind massif test jobs to get approximate peak memory usage for a
'Hello world' test (involving startup RAM usage + minimal compilation
memory usage).
* Add Minisphere and DukLuv as initial examples of third party builds as
regression tests.
* Fix apitest executor, other minor fixes.