[Vulkan] Add -Os flag to shader compilation (#57199)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57199
Reduces the size of compiled shaders, and also potentially adds some performance boost.
Test Plan: Imported from OSS
Reviewed By: xta0
Differential Revision: D28293816
Pulled By: SS-JIA
fbshipit-source-id: 424dc0bce24d6115ba2bf8405027e967f6cb9497
