Prepare for upcoming shared makefile change
RiscOS/BuildSys!62 (merged) will change how top-level phony rules are overridden.
In this component, the install, install_rom, rom and standalone
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