Add a unit test for #5584 (#5604)

tests/unit/src/unit/issues/Issue5584.hx

@@ -0,0 +1,17 @@
+package unit.issues;
+
+import cpp.Callable;
+import cpp.Object;
+import haxe.io.Bytes;
+
+class Issue5584 extends Test {
+	function test() {
+		var callable = new Callable<Object->Object>(cffi_decompress);
+		var bytes = Bytes.alloc (100);
+		var data:Dynamic = callable.call (bytes);
+	}
+
+	function cffi_decompress(a:Dynamic):Dynamic {
+		return null;
+	}
+}