Prepare for upcoming shared makefile change
RiscOS/BuildSys!62 (merged) will change how top-level phony rules are overridden.
In this component, the standalone target in the Sources/utils makefile
is redefined after AAsmModule is included, so it 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