f3c83dbd8d
Before, we created invalid directory paths when the host directory was
"/", and now we don't!
This brings tests left failing on GOOS=js to 7
```bash
$ wazero run -mount=/:/ --experimental-workdir=$(go env GOROOT)/src/os os.wasm| grep '^--- FAIL'|wc -l
7
```
See #1222
Signed-off-by: Edoardo Vacchi <evacchi@users.noreply.github.com>
Co-authored-by: Edoardo Vacchi <evacchi@users.noreply.github.com>