Turbopack: delete .next folder before throwing due to "pages/app directory must be in the same folder" (#84553)

### What?

I expect an empty .next folder after an error, so it should delete it before doing the check, so that an error doesn't result in a stale .next folder

Author: sokra

packages/next/src/build/index.ts

@@ -1016,6 +1016,34 @@ export default async function build(
       NextBuildContext.originalRewrites = config._originalRewrites
       NextBuildContext.originalRedirects = config._originalRedirects
 
+      const distDirCreated = await nextBuildSpan
+        .traceChild('create-dist-dir')
+        .traceAsyncFn(async () => {
+          try {
+            await fs.mkdir(distDir, { recursive: true })
+            return true
+          } catch (err) {
+            if (isError(err) && err.code === 'EPERM') {
+              return false
+            }
+            throw err
+          }
+        })
+
+      if (!distDirCreated || !(await isWriteable(distDir))) {
+        throw new Error(
+          '> Build directory is not writeable. https://nextjs.org/docs/messages/build-dir-not-writeable'
+        )
+      }
+
+      if (config.cleanDistDir && !isGenerateMode) {
+        await nextBuildSpan
+          .traceChild('clean')
+          .traceAsyncFn(() =>
+            recursiveDeleteSyncWithAsyncRetries(distDir, /^(cache|dev)/)
+          )
+      }
+
       const cacheDir = getCacheDir(distDir)
 
       const telemetry = new Telemetry({ distDir })
@@ -1102,34 +1130,6 @@ export default async function build(
         cacheDir,
       }
 
-      const distDirCreated = await nextBuildSpan
-        .traceChild('create-dist-dir')
-        .traceAsyncFn(async () => {
-          try {
-            await fs.mkdir(distDir, { recursive: true })
-            return true
-          } catch (err) {
-            if (isError(err) && err.code === 'EPERM') {
-              return false
-            }
-            throw err
-          }
-        })
-
-      if (!distDirCreated || !(await isWriteable(distDir))) {
-        throw new Error(
-          '> Build directory is not writeable. https://nextjs.org/docs/messages/build-dir-not-writeable'
-        )
-      }
-
-      if (config.cleanDistDir && !isGenerateMode) {
-        await nextBuildSpan
-          .traceChild('clean')
-          .traceAsyncFn(() =>
-            recursiveDeleteSyncWithAsyncRetries(distDir, /^(cache|dev)/)
-          )
-      }
-
       if (appDir && 'exportPathMap' in config) {
         Log.error(
           'The "exportPathMap" configuration cannot be used with the "app" directory. Please use generateStaticParams() instead.'

packages/next/src/lib/recursive-delete.ts

@@ -74,7 +74,7 @@ export async function recursiveDeleteSyncWithAsyncRetries(
   dir: string,
   /** Exclude based on relative file path */
   exclude?: RegExp,
-  /** Ensures that parameter dir exists, this is not passed recursively */
+  /** Relative path to the directory being deleted, used for exclude */
   previousPath: string = ''
 ): Promise<void> {
   let result