Change Details

``` make -C audio/abx -V _WITH_TESTING make -C audio/abx -V _WITH_TESTING WITH_TESTING=yes yes make -C audio/abx -V _WITH_TESTING WITH_TESTING=yes WITHOUT_TESTING_PORTS=audio/abx ```

Tested the feature itself on `devel/zfp` (that has `USES=cmake:testing`) and `graphics/ImageMagick7` (which has just `TEST_TARGET`). Tested WITH/WITHOUT stuff the following way: ``` make -C audio/abx -V _WITH_TESTING make -C audio/abx -V _WITH_TESTING WITH_TESTING=yes yes make -C audio/abx -V _WITH_TESTING WITH_TESTING=yes WITHOUT_TESTING_PORTS=audio/abx ```

Tested the feature itself on `devel/zfp` (that has `USES=cmake:testing`) and `graphics/ImageMagick7` (which has just `TEST_TARGET`). Tested WITH/WITHOUT stuff the following way: ``` make -C audio/abx -V _WITH_TESTING make -C audio/abx -V _WITH_TESTING WITH_TESTING=yes yes make -C audio/abx -V _WITH_TESTING WITH_TESTING=yes WITHOUT_TESTING_PORTS=audio/abx ```