fixup! fix(@angular/build): conditionally declare tslib in built library package

Author: alan-agius4

packages/angular/build/src/builders/library/pipeline/package-manifests.ts

@@ -191,7 +191,7 @@ let cachedTslibRange: string | undefined;
  * @returns tslib range
  */
 function getAngularTslibRange(workspaceRoot: string): string {
-  if (cachedTslibRange !== undefined) {
+  if (cachedTslibRange) {
     return cachedTslibRange;
   }