Tweak sys_argv override as late-binding so that sys.argv is looked up as late as possible.
Tweak sys_argv override as late-binding so that sys.argv is looked up as late as possible.

In some multiprocessing use cases sys.argv isn't correctly populated in the forked process until much later. Saving a reference at flag creation time may use the wrong reference to sys.argv, so lookup sys.argv at parse time.

PiperOrigin-RevId: 457429854
Change-Id: I7da43e44c7ee8c982a71d6406360305dd1539f7a

google/ml_collections,google/ml_collections