As a preparation for the introduction of the 'atarixl' target it is
necessary that all drivers have a base name...
- no longer than 7 characters
- with a common prefix
- No complex shell logic.
- "Source file shadowing" for all targets via vpath.
- Dependency handling.
- True incremental build.
- Don't write into source directories.
- Easy cleanup by just removing 'wrk'.
