Sys.command fails when using quotes

The following command fails for no reason:

```haxe
Sys.command(' "path/to/some.exe" --arg "quotedArgument" ');
```
This seems to be related to the presence of double-quotes around *both* exe path and argument.

**Workaround**: use `sys.io.Process`:
```haxe
var p = new sys.io.Process(' "path/to/some.exe" --arg "quotedArgument" '); // identical command
p.close();
```

For some reason, it seems like `Sys.command` implementation differs from `sys.io.Process` 🤔

Start by comparing the Sys.command and sys.io.Process entry points using the quoted command shown in the issue. Reproduce the failure and inspect why the two implementations handle quotes differently; done means the command with both a quoted executable path and quoted argument succeeds consistently.

Written by the indexing model from the issue text.