Add support for Arm tests on MacOS (#5786)

Summary:
Check which platform is used for the extension of the quantization lib and select extensions for dynamic libraries accordingly.

Change-Id: I7e4afcccf7f7d8de7416a83e9bfe4511a6540912

Pull Request resolved: https://github.com/pytorch/executorch/pull/5786

Reviewed By: mergennachin

Differential Revision: D63808512

Pulled By: digantdesai

fbshipit-source-id: b27f116605b3d1480049d3b47461b96bcab71bab