Fix test_jit_cuda_archflags on Windows (#93332)
Fixes https://github.com/pytorch/pytorch/issues/61655
The test is flaky and fails whenever `test_jit_cuda_archflags` is run. The latter `test_jit_cuda_archflags` was slow test in the old Windows runner. It's currently running again on trunk due to the problem with populating slow-test JSON file ~Interestingly, its performance is getting better in the new Windows G5 runner and it becomes a borderline slow test, where it run sometimes~. Whenever it runs, the next test `test_jit_cuda_extension` will fail.
* Build and load different CUDA arch modules from `test_jit_cuda_archflags` in separate processes to avoid importing them into the current one. The test only checks the build artifacts. Importing them cause `test_jit_cuda_extension` to fail as describe in https://github.com/pytorch/pytorch/issues/61655
* Clean up the temp build dir on Windows. Windows CUDA runner is non-ephemeral, so it's better to clean thing up properly to avoid any funny business the next time the runner is used
Pull Request resolved: https://github.com/pytorch/pytorch/pull/93332
Approved by: https://github.com/davidberard98
