[CMake] ctest, timeout per test/cmd

[Ken Martin]

> The problem with DART_TESTING_TIMEOUT and CTEST_TEST_TIMEOUT is that
> they apply to the complete test suites. What I'm trying to solve is
> some infinite loops test cases, I like the tests to fail/timeout but
> the next tests should be executed as well.

Just to make sure we are on the same page :) DART_TESTING_TIMEOUT applies to
each test. Once one times out the next will start. It is not a limit for the
entire process but for each test. Each test is given DART_TESTING_TIMEOUT
seconds to complete independent of the time any other test took to run.

Ken