AMD in bundles to use "bundle" meta over "register" format meta

compilers/amd.js

@@ -324,9 +324,8 @@ exports.compile = function(load, opts, loader) {
 
   // because we've blindly replaced the define statement from AMD with a System.registerDynamic call
   // we have to ensure we still trigger any AMD guard statements in the code by creating a dummy define which isn't called
-  // "register" added to ensure AMD at the top of a bundle allows the bundle to be detected properly
   return Promise.resolve({
-    source: '"format register";(function() {\nvar _removeDefine = System.get("@@amd-helpers").createDefine();\n' + output + '\n_removeDefine();\n})();',
+    source: '(function() {\nvar _removeDefine = System.get("@@amd-helpers").createDefine();\n' + output + '\n_removeDefine();\n})();',
     sourceMap: compiler.getSourceMap(),
     sourceMapOffset: 2
   });

lib/compile.js

@@ -155,6 +155,17 @@ function compileOutputs(loader, tree, opts, sfxEntryPoints, cache) {
     }));
   })
 
+  // if any module in the bundle is AMD, add a "bundle" meta to the bundle
+  // this can be deprecated if https://github.com/systemjs/builder/issues/264 lands
+  .then(function() {
+    var hasAMD = modules.some(function(name) {
+      return tree[name].format == 'amd';
+    });
+
+    if (hasAMD)
+      outputs.unshift('"bundle"');
+  })
+
   .then(function() {
     if (sfxEntryPoints)
       return wrapSFXOutputs(loader, tree, outputs, sfxEntryPoints, opts);