backport: Only filter next config if experimental flag is enabled (#88733) (#88772)

Backports #88733

Co-authored-by: Niklas Mischkulnig <[email protected]>

Author: ijjk

packages/next/src/build/index.ts

@@ -1852,11 +1852,15 @@ export default async function build(
             }
           }
 
+          // getNextConfigRuntime only filters if experimental.runtimeServerDeploymentId is true,
+          // but we unconditionally want to remove configFile for this manifest
+          let runtimeConfigWithoutFilePath = { ...runtimeConfig }
+          delete (runtimeConfigWithoutFilePath as NextConfigComplete).configFile
+
           const serverFilesManifest: RequiredServerFilesManifest = {
             version: 1,
             config: {
-              ...runtimeConfig,
-
+              ...runtimeConfigWithoutFilePath,
               ...(ciEnvironment.hasNextSupport
                 ? {
                     compress: false,

packages/next/src/server/config-shared.ts

@@ -1683,6 +1683,11 @@ export interface NextConfigRuntime {
 export function getNextConfigRuntime(
   config: NextConfigComplete | NextConfigRuntime
 ): NextConfigRuntime {
+  // This config filter is a breaking change, so only do it if experimental.runtimeServerDeploymentId is enabled
+  if (!config.experimental.runtimeServerDeploymentId) {
+    return config
+  }
+
   let ex = config.experimental
 
   type Requiredish<T> = {