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`.
4610093c87/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;
 }