file-roller: fix test crash without window server (#4330)

`file-roller --version` dies when not logged into the macOS GUI with
```
  *** -[__NSArray0 objectAtIndex:]: index 0 beyond bounds for empty
  NSArray
```

So use `--help` instead.

Formula/file-roller.rb

@@ -53,6 +53,6 @@ class FileRoller < Formula
   end
 
   test do
-    assert_match version.to_s, shell_output("#{bin}/file-roller --version 2>&1")
+    system bin/"file-roller", "--help"
   end
 end