Testcppextensionjit rebuild once (#40169)
Summary:
Previous:
deco dont_wipe_extensions_build_folder control clean build path or not.
Now:
If cpp files or args changed, rebuild extension. clean build path only before and after test suite.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/40169
Differential Revision: D22161450
Pulled By: ezyang
fbshipit-source-id: 9167c8265e13922f68cd886be900f84ffc6afb84
