add empty contract

samples/empty_contract.rs

@@ -0,0 +1,12 @@
+#![feature(link_args)]
+#![no_main]
+
+// as it is experimental preamble
+#![allow(dead_code)]
+
+#[link_args = "-s WASM=1 -s NO_EXIT_RUNTIME=1 -s NO_FILESYSTEM=1 -s"]
+extern {}
+
+#[no_mangle]
+pub fn call() {
+}