fix: skip rendering dynamic root segment routes (vercel#74039)

Routes that contain dynamic root segments (those where the root
parameter is not known at build time) should not have shells generated.
This is because today there's no way to revalidate the shell for that
page and it would cause cache posioning.

packages/next/src/build/index.ts

@@ -2788,6 +2788,16 @@ export default async function build(
                   : undefined
 
                 routes.forEach((route) => {
+                  // If the route has any dynamic root segments, we need to skip
+                  // rendering the route. This is because we don't support
+                  // revalidating the shells without the parameters present.
+                  if (
+                    route.fallbackRootParams &&
+                    route.fallbackRootParams.length > 0
+                  ) {
+                    return
+                  }
+
                   defaultMap[route.pathname] = {
                     page: originalAppPath,
                     query: { __nextSsgPath: route.encodedPathname },