misc/wasm: wasm_exec: non-zero exit code on compile error

Return a non-zero exit code if the WebAssembly host fails to compile
the WebAssmbly bytecode to machine code.

Change-Id: I774309db2872b6a2de77a1b0392608058414160d
Reviewed-on: https://go-review.googlesource.com/110097Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

misc/wasm/wasm_exec.js

@@ -38,6 +38,7 @@ if (typeof process !== "undefined") { // detect Node.js
 
 	compileAndRun(fs.readFileSync(process.argv[2])).catch((err) => {
 		console.error(err);
+		process.exit(1);
 	});
 } else {
 	window.global = window;