Prepare for upcoming shared makefile change
RiscOS/BuildSys!62 (merged) will change how top-level phony rules are overridden.
In this component, the install_rom and rom targets are redefined after
AAsmModule is included, so they will be affected. Rewrite the rules so
that they will continue to work the same (at least for native builds) both
before and after BuildSys is updated.
!NoChange