Make build fail if first level subdirectory fails The build process was ignoring a failed target and kept on building others. For instance, If NITROS9DIR was not set and there was no $HOME/nitros9 the build would spiral down in infinite make recursion instead of just quit on first failure (at least for some targets). Now all listed subdirectories must build successfully. This change should be generalized to lower level directories as well. Also add some dummy targets where appropriate so that the build does not fail where nothing really should be built.