Revoke test execution for extra-cmake-modules across all platforms.

The tests in their current condition are incompatible with being run prior to installation, and leave the build directory unusable following their execution.
This means that brokeness in ECM won't be seen anywhere in the CI system until it is picked up the Dependency Rebuild jobs, after which point the impact will be KDE wide.
To ensure that the rest of Frameworks is built using the most recent version of ECM - and thus ensure any brokeness in ECM is detected early - we skip running tests, which allows installation to succeed.

CCMAIL: kde-frameworks-devel@kde.org
CCMAIL: release-team@kde.org