Change:
- Use `chmod +a` in the fallback chain to allow MacOS to use ACLs to
allow an unprivileged user to become an unprivileged user.
Test Plan:
- CI, new tests
Tickets:
- Fixes#70648
Signed-off-by: Rick Elrod <rick@elrod.me>
Change:
- Refactoring to make it harder to get wrong and easier to read.
- Generalize become_unprivileged tests and fix some that never worked
but also never failed.
Test Plan:
- CI, new units/integration tests
Signed-off-by: Rick Elrod <rick@elrod.me>