Add buck config to remove ET_LOG (#569)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/569

|**build, stripped** | **x86_64 (devserver)** | **arm64 (macbook)** |
|With ET_LOG, verification | 82576 | 122376 |
|Without ET_LOG | 67576 | 105720 |
|Without ET_LOG, verification | 48584 |  89280|

Reviewed By: larryliu0820

Differential Revision: D49709986

fbshipit-source-id: d68c101738eb6395b30c5741c879d94a435684ec