rustup

a6635323 - test(cli/self-upd): use direct arg0 override for `as_rustup_setup()`

test(cli/self-upd): use direct arg0 override for `as_rustup_setup()` This prevents a random error on Linux when running the test on CI. Sometimes, even after `fs::copy()` has returned, the executable is still considered "busy" by the OS, causing the test to fail with: ```rust Os { code: 26, kind: ExecutableFileBusy, message: "Text file busy" } ``` This change avoids that by using a direct arg0 override instead.