Fix experimental optimizeCss for SSR (#22513)

This ensures `distDir` is set under `renderOpts` in `next-server` so that it is present when experimental `optimizeCss` is enabled. 

x-ref: https://github.com/vercel/next.js/pull/16539

packages/next/next-server/server/next-server.ts

@@ -161,6 +161,7 @@ export default class Server {
     locales?: string[]
     defaultLocale?: string
     domainLocales?: DomainLocales
+    distDir: string
   }
   private compression?: Middleware
   private onErrorMiddleware?: ({ err }: { err: Error }) => Promise<void>
@@ -218,6 +219,7 @@ export default class Server {
       optimizeImages: this.nextConfig.experimental.optimizeImages,
       optimizeCss: this.nextConfig.experimental.optimizeCss,
       domainLocales: this.nextConfig.i18n?.domains,
+      distDir: this.distDir,
     }
 
     // Only the `publicRuntimeConfig` key is exposed to the client side

test/integration/critical-css/pages/index.js

@@ -8,4 +8,10 @@ export default function Home() {
   )
 }
 
-Home.getInitialProps = () => ({})
+export const getServerSideProps = () => {
+  return {
+    props: {
+      hello: 'world',
+    },
+  }
+}

test/integration/critical-css/test/index.test.js

@@ -19,7 +19,7 @@ let app
 
 function runTests() {
   it('should inline critical CSS', async () => {
-    const html = await renderViaHTTP(appPort, '/index')
+    const html = await renderViaHTTP(appPort, '/')
     expect(html).toMatch(
       /<link rel="stylesheet" href="\/_next\/static\/css\/.*\.css" .*>/
     )
@@ -27,7 +27,7 @@ function runTests() {
   })
 
   it('should not inline non-critical css', async () => {
-    const html = await renderViaHTTP(appPort, '/index')
+    const html = await renderViaHTTP(appPort, '/')
     expect(html).not.toMatch(/.extra-style/)
   })
 }