build system --disable-unittests has no effect

While I applaud the explosion of unit test code in recent versions, I do not possess the hardware resources or time for running them and am unlikely to ever do so. To the extent that one would run tests, it's no problem at all to explicitly build them as needed.

Please cause the --disable-unittests option of configure to function as one would expect. Building test code takes a long time and I see no obvious Makefile hack to turn it off.