Add support for global externals in Electron

Author: rhysd

lib/index.js

@@ -36,6 +36,7 @@ var fs = require('fs');
 var exists = fs && fs.existsSync;
 var resolve = path && path.resolve;
 var isWindows;
+var isElectron;
 var isGlobal;
 var globals;
 var cwd;
@@ -49,7 +50,8 @@ if (typeof global !== 'undefined') {
 
     /* Detect whether we’re running as a globally installed package. */
     isWindows = global.process.platform === 'win32';
-    isGlobal = global.process.argv[1].indexOf(npmPrefix) === 0;
+    isElectron = global.process.versions.electron !== undefined;
+    isGlobal = isElectron || global.process.argv[1].indexOf(npmPrefix) === 0;
 
     /* istanbul ignore next */
     globals = resolve(npmPrefix, isWindows ? '' : 'lib', MODULES);