buildroot

package/pkg-cmake.mk: disable colouring the output

Because cmake was the only build-system supporting this feature, it has been
disabled for the target packages.
For consistency, this patch does the same for host package too.

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>