message: fix(ivy): should not overwrite an existing ngInjectableDef
  There is no test in this diff because I've made a failing test pass.
  PR Close
diff: @@ -27,6 +27,10 @@ export function compileInjectable(type: Type<any>, srcMeta?: Injectable): void {
  const meta: Injectable = srcMeta || {providedIn: null};
  let def: any = null;
  +
  + // if NG_INJECTABLE_DEF is already defined on this class then don't overwrite it
  + if (type.hasOwnProperty(NG_INJECTABLE_DEF)) return;
  +
  Object.defineProperty(type, NG_INJECTABLE_DEF, {
  get: () => {
  if (def === null) {
  