Remove ET_LOG and verification from OSS Release build (#509)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/509

Removing ET_LOG and verification from OSS Release build.

|**build, stripped** | **x86_64 (devserver)** | **arm64 (macbook)** |
| With ET_LOG, verification | 72232 | 89544 |
| Without ET_LOG | 51728 | 72712 |
| Without ET_LOG, verification | 39440 |  56072|

Reviewed By: dbort

Differential Revision: D49708709

fbshipit-source-id: 817d98d4b96bbd0dbb14eea1f0e759a3dff2a966