fix: next dynamic with jest (vercel#26614)

Fixes vercel#19862

Avoid executing `webpack` property on `loadableGenerated` of loadable component compiled from `next/dynamic` when `require.resolveWeak` is unavailable due to jest runtime missing `require.resolveWeak`.

## Bug

- [x] Related issues linked using `fixes #number`
- [x] unit tests added

packages/next/next-server/lib/loadable.js

@@ -94,7 +94,8 @@ function createLoadableComponent(loadFn, options) {
   if (
     !initialized &&
     typeof window !== 'undefined' &&
-    typeof opts.webpack === 'function'
+    typeof opts.webpack === 'function' &&
+    typeof require.resolveWeak === 'function'
   ) {
     const moduleIds = opts.webpack()
     READY_INITIALIZERS.push((ids) => {

test/unit/fixtures/stub-components/hello.js

@@ -0,0 +1,5 @@
+import React from 'react'
+
+export default function Hello() {
+  return <div>hello</div>
+}

test/unit/next-dynamic.test.js

@@ -0,0 +1,16 @@
+/**
+ * @jest-environment jsdom
+ */
+import React from 'react'
+import { act, render } from '@testing-library/react'
+import dynamic from 'next/dynamic'
+
+describe('next/dynamic', () => {
+  it('test link with unmount', () => {
+    const App = dynamic(() => import('./fixtures/stub-components/hello'))
+    act(() => {
+      const { unmount } = render(<App />)
+      unmount()
+    })
+  })
+})