community/libkexiv2-kf5: disable check due to no tests

The `tests/` directory compiles some executables to `build/bin/` but
they do not appear to be part of an automated test suite. No sample
files are provided with the executables to run tests.

Disable check to avoid `No tests were found!!!` error causing build
failure with abuild 3.14.0.

Ref: #16519