Keep special files

Cray compiler can produce `.lst` files for each file compiled. Maybe keep them next to the `.o` files. Maybe also keep compiler stdout/stderr output there too. How would this affect disc usage?

No source files, tests, or entry points are named. Begin by locating how fab handles compiler-generated .o artifacts and Cray compiler output, then establish whether .lst files and stdout/stderr should be retained and assess the disk-use impact.

Written by the indexing model from the issue text.