RFC: Enabling -DKDE4_BUILD_TESTS=ON by default

[Laszlo Papp]

> 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.

I have just checked few packagings, and perhaps if they do not have
issues with the tests, the communication was not good enough between
the developers and packagers. This change may help with that, but it
should also be communicated with the packagers to get them aware about
the change.

Laszlo