ignore EEXIST errors when creating symlinks for output standalone (ve…

…rcel#40150)

I think the `EEXIST` error may be because next already copies some files here
https://github.com/vercel/next.js/blob/e91cbcc03d7226cc6f2edb66c656ae08bdf5b903/packages/next/build/index.ts#L2442


partially fixes vercel#36386 when using pnpm linker

## Bug

- [x] Related issues linked using 
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

packages/next/build/utils.ts

@@ -1371,7 +1371,13 @@ export async function copyTracedFiles(
           const symlink = await fs.readlink(tracedFilePath).catch(() => null)
 
           if (symlink) {
-            await fs.symlink(symlink, fileOutputPath)
+            try {
+              await fs.symlink(symlink, fileOutputPath)
+            } catch (e: any) {
+              if (e.code !== 'EEXIST') {
+                throw e
+              }
+            }
           } else {
             await fs.copyFile(tracedFilePath, fileOutputPath)
           }