refactor(elements): add accessor workaround for build-optimizer (angular#37456)

Build-optimizer currently uses TypeScript 3.6 which is unable to resolve an 'accessor' in 'getTypeOfVariableOrParameterOrPropertyWorker'.

Unfortunately, in Build optimizer we cannot update the version of TypeScript because of microsoft/TypeScript#38412

PR Close angular#37456

Author: alan-agius4

packages/elements/src/create-custom-element.ts

@@ -213,7 +213,11 @@ export function createCustomElement<P>(
   // compliance with the spec). This breaks emulated inheritance in ES5 on environments that do not
   // natively support `Object.setPrototypeOf()` (such as IE 9-10).
   // Update the property descriptor of `NgElementImpl#ngElementStrategy` to make it enumerable.
-  Object.defineProperty(NgElementImpl.prototype, 'ngElementStrategy', {enumerable: true});
+  // The below 'const', shouldn't be needed but currently this breaks build-optimizer
+  // Build-optimizer currently uses TypeScript 3.6 which is unable to resolve an 'accessor'
+  // in 'getTypeOfVariableOrParameterOrPropertyWorker'.
+  const getterName = 'ngElementStrategy';
+  Object.defineProperty(NgElementImpl.prototype, getterName, {enumerable: true});
 
   // Add getters and setters to the prototype for each property input.
   defineInputGettersSetters(inputs, NgElementImpl.prototype);