Summary:
**Changes**
* Deleted function import from build definition utilities
* Removed `load("//tools/build_defs:fbsource_utils.bzl", "is_arvr_mode")`
* Replaced is_arvr_mode() function calls with direct references to configuration flags
* Changed from `is_arvr_mode()` to `"ovr_config//build_mode:arvr_mode"`
* Changed conditional expressions to Buck `select()` statements
Test Plan:
Check if CI passes
Rollback Plan:
Differential Revision: D78520947
Pull Request resolved: https://github.com/pytorch/pytorch/pull/158682
Approved by: https://github.com/malfet