Add option to specify environment variables for MAST in the extra args field

Summary: Pull Request resolved: https://github.com/facebookresearch/d2go/pull/486

Reviewed By: frabu6

Differential Revision: D43538416

fbshipit-source-id: ca323dff0ae3b0dee1eccac3c4f8b95d01c6e5d9

d2go/runner/config_defaults.py

@@ -33,6 +33,11 @@ def _add_detectron2go_runner_default_fb_cfg(_C: CN) -> None:
     pass
 
 
+@fb_overwritable()
+def _add_base_runner_default_fb_cfg(_C: CN) -> None:
+    pass
+
+
 def _add_detectron2go_runner_default_cfg(_C: CN) -> None:
     # _C.MODEL.FBNET_V2...
     add_fbnet_v2_default_configs(_C)
@@ -146,6 +151,8 @@ def get_base_runner_default_cfg(cfg: CN) -> CN:
     # run evaluation after training is done
     cfg.TEST.FINAL_EVAL = True
 
+    _add_base_runner_default_fb_cfg(cfg)
+
     return cfg