Cannot make `executable` required.

[jjotero]

If the excutable variable is required it will always be initialised by ReFrame in the pipeline's __rfm_init__ method to the test's name. Whereas that is absolutely fine for either RegressionTest or CompileOnlyRegressionTest, this behaviour should not occur with RunOnlyRegressionTest classes, where the user should have the full power on requiring the executable variable.

Possible workaround: move this default assignment into the compile stage.

[vkarak]

Possible workaround: move this default assignment into the compile stage.

I think that't the best thing and along the general idea that we set the variables as close as possible to their use. In tests that need to compile the code with SingleSource, this is the compile phase, otherwise it's the run phase.