RFC: Enabling -DKDE4_BUILD_TESTS=ON by default

[Laszlo Papp]

> +1 for always building unit tests!
> Actually I've always been unsure why packagers don't run unit tests...
> Maybe this would help.

Because the tests are broken in certain environments (just like last
time on Harmattan with the frameworks branch) and due to the lack of
time on the packagers' side to fix upstream bugs, they choose the
simpler way as a temporary workaround. Therefore, they can proceed
with the project, and do other things further on.

+1 from me as well for sure! :-)

Laszlo