Fix race condition when creating build dir (#30956)
Summary:
The original `check-and-act` style can raise `FileExistsError` when multiple processes are jit-compiling the extension on the same node.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30956
Differential Revision: D19262570
Pulled By: ezyang
fbshipit-source-id: bb18c72e42648770b47f9378ac7c3929c3c03efc
