The ported code in 80ebc55 was incorrectly ported.

```
-            $envCommand = "exec $execArgs $interpreter -e 'load(\"$script\")' -- ${\(join ' ', (map shellEscape, @savedArgs))}";
...
+                    envCommand = (format("exec %1% %2% -e 'load(\"%3%\") -- %4%") % execArgs % interpreter % script % joined.str()).str();
```

The single-quote finishing the small ruby snippet was lost in
translation.

The test fakes the interpreter only to verify the arguments it would be
given.

... in the ruby shebang test.