Fix process spawning on Windows

build-system/common/exec.js

@@ -39,14 +39,17 @@ function exec(cmd, options = {'stdio': 'inherit'}) {
 }
 
 /**
- * Executes the provided shell script in an asynchronous process.
+ * Executes the provided shell script in an asynchronous process. Special-cases
+ * the AMP task runner so that it is correctly spawned on all platforms (node
+ * shebangs do not work on Windows).
  *
  * @param {string} script
  * @param {?Object} options
  * @return {!childProcess.ChildProcessWithoutNullStreams}
  */
 function execScriptAsync(script, options) {
-  return childProcess.spawn(script, {shell: shellCmd, ...options});
+  const scriptToSpawn = script.startsWith('amp ') ? `node ${script}` : script;
+  return childProcess.spawn(scriptToSpawn, {shell: shellCmd, ...options});
 }
 
 /**

build-system/common/process.js

@@ -26,13 +26,16 @@ const shellCmd = process.platform == 'win32' ? 'cmd' : '/bin/bash';
 
 /**
  * Spawns the given command in a child process with the given options.
+ * Special-cases the AMP task runner so that it is correctly spawned on all
+ * platforms (node shebangs do not work on Windows).
  *
  * @param {string} cmd
  * @param {?Object} options
  * @return {!Object}
  */
 function spawnProcess(cmd, options) {
-  return childProcess.spawnSync(cmd, {shell: shellCmd, ...options});
+  const cmdToSpawn = cmd.startsWith('amp ') ? `node ${cmd}` : cmd;
+  return childProcess.spawnSync(cmdToSpawn, {shell: shellCmd, ...options});
 }
 
 /**