This should fix the following error showing up on MacOS:
```
error: assertion ((__lessThan 0) ((builtins).stringLength watchmanSockPath))
failed at /Users/jenkins/repos/status-react/nix/mobile/android/watchman.nix:8:9
```
Which was caused by flags like `--argstr` not being passed.
Signed-off-by: Jakub Sokołowski <jakub@status.im>