compiler: add a test case to ensure more stable local modules

compiler/tests/local/local.v

@@ -0,0 +1,7 @@
+
+module local
+
+pub fn local_fn() bool {
+  return true
+}
+

compiler/tests/local_test.v

@@ -0,0 +1,7 @@
+
+import compiler.tests.local
+
+fn test_local_module_is_callable() {
+  assert local.local_fn()
+}
+