[ECS] How to share a single GPU with multiple containers

### Summary

I'd like to share the single GPU of a p3.2xlarge instance with multiple containers in the same task.

### Description

In the ECS task definition it's not possible to indicate a single GPU can be shared between containers (or to distribute the GPU resource over multiple containers like with CPU units).

I have multiple containers that require a GPU but not at the same time. Is there a way run them in a single task on the same instance?
I've tried leaving the GPU unit resource blank but then the GPU device is not visible to the container.