Merge pull request #746 from bettio/fix-hello-world

Fix hello_world and "Install and smoke test"

Explicitly return ok, so atomvm exits with success.

For reference:
```c
114     int status;
115     if (ret_value == OK_ATOM) {
116         status = EXIT_SUCCESS;
117     } else {
118         status = EXIT_FAILURE;
119     }
```

These changes are made under both the "Apache 2.0" and the "GNU Lesser General
Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

examples/erlang/hello_world.erl

@@ -22,4 +22,5 @@
 -export([start/0]).
 
 start() ->
-    erlang:display(hello_world).
+    erlang:display(hello_world),
+    ok.