fix(core): set ngDevMode to false when calling enableProdMode() (…

…#40124)

The `ngDevMode` description also mentions that calling `enableProdMode` will set this the value to `false`.
https://github.com/angular/angular/blob/4610093c87975b6355f31a9c849351129908783a/packages/core/src/util/ng_dev_mode.ts#L22 which is currently not the case.

PR Close #40124

packages/core/src/util/is_dev_mode.ts

@@ -6,6 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {global} from './global';
+
 /**
  * This file is used to control if the default rendering pipeline should be `ViewEngine` or `Ivy`.
  *
@@ -44,5 +46,12 @@ export function enableProdMode(): void {
   if (_runModeLocked) {
     throw new Error('Cannot enable prod mode after platform setup.');
   }
+
+  // The below check is there so when ngDevMode is set via terser
+  // `global['ngDevMode'] = false;` is also dropped.
+  if (typeof ngDevMode === undefined || !!ngDevMode) {
+    global['ngDevMode'] = false;
+  }
+
   _devMode = false;
 }