Arm backend: Simplify linking in example executor_runner (#21491)

- Do not use --whole-archive unless needed.
- Remove targets that are linked from other target.

Removes some complexity and noise.

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils
@Sebastian-Larsson @robell @rascani

Signed-off-by: Erik Lundell <erik.lundell@arm.com>