[CMake] [CMAKE] Disable testing when building using bootstrap

[Jon Haitz Legarreta Gorroño]

Hi,

I'm trying to build CMake from sources using the `bootstrap` script.

Please, correct me if I'm wrong, but it looks like CMake is being
built with `BUILD_TESTING=ON` by default.

I'd like to disable testing (and any other non-essential option), but
AFAIK bootstrap does not expose the `-DBUILD_TESTING` flag, or I have
not found a way to set it to `OFF`.

Is this possible / does this make sense at all? Can anyone please
provide me with the pointers to do so?

Thank you,
JON HAITZ