Pass more size-shrinking options to wasm-opt (#212)

Author: tomaka

bin/wasm-node/javascript/prepare.js

@@ -34,7 +34,7 @@ child_process.execSync(
 // use the `.wasm` generated by the Rust compiler.
 try {
     child_process.execSync(
-        "wasm-opt -o autogen/tmp.wasm -O ../../../target/wasm32-wasi/release/substrate_lite_js.wasm",
+        "wasm-opt -o autogen/tmp.wasm -Os --strip-debug --vacuum --dce ../../../target/wasm32-wasi/release/substrate_lite_js.wasm",
         { 'stdio': 'inherit' }
     );
 } catch(error) {