Use next-swc from branch for PR size stats (#66964)

Currently, PR stats are always downloading published binaries:

> cd /tmp/next-statsJoJEbE/stats-app && NEXT_TELEMETRY_DISABLED=1 pnpm
next build
> [...]
> Downloading swc package @next/swc-linux-x64-gnu...

--
https://github.com/vercel/next.js/actions/runs/9505097022/job/26199227309#step:7:1713

## test plan
- [x] Makes #66711 go green
- [x] `GIT_ROOT_DIR=https://github.com/ GITHUB_REPOSITORY=vercel/next.js
GITHUB_REF=sebbie/06-10-update_react_from_1df34bdf62_to_20b6f4c0e8
GITHUB_ACTION=synchronize node
.github/actions/next-stats-action/src/index.js` completes `pnpm build`
(but fails afterwards locally which is expected)

.github/actions/next-stats-action/native/.gitignore

@@ -0,0 +1,4 @@
+# Ignore everything in this directory
+*
+# Except this file
+!.gitignore

.github/actions/next-stats-action/src/prepare/repo-setup.js

@@ -65,7 +65,11 @@ module.exports = (actionInfo) => {
      * @param {{ repoDir: string, nextSwcVersion: null | string }} options Required options
      * @returns {Promise<Map<string, string>>} List packages key is the package name, value is the path to the packed tar file.'
      */
-    async linkPackages({ repoDir, nextSwcVersion, parentSpan }) {
+    async linkPackages({
+      repoDir,
+      nextSwcVersion: nextSwcVersionSpecified,
+      parentSpan,
+    }) {
       if (!parentSpan) {
         // Not all callers provide a parent span
         parentSpan = mockSpan()
@@ -118,6 +122,11 @@ module.exports = (actionInfo) => {
         }
       })
 
+      const nextSwcVersion =
+        nextSwcVersionSpecified ??
+        pkgDatas.get('@next/swc')?.packedPackageTarPath ??
+        null
+
       await parentSpan
         .traceChild('write-packagejson')
         .traceAsyncFn(async () => {
@@ -171,9 +180,11 @@ module.exports = (actionInfo) => {
               })
               if (nextSwcVersion) {
                 Object.assign(packageJson.dependencies, {
+                  // CI
                   '@next/swc-linux-x64-gnu': nextSwcVersion,
+                  // Vercel issued laptops
+                  '@next/swc-darwin-arm64': nextSwcVersion,
                 })
-              } else {
               }
             }
 

test/.stats-app/package.json

@@ -3,7 +3,7 @@
   "private": true,
   "license": "MIT",
   "dependencies": {
-    "next": "19.0.0-rc-6230622a1a-20240610",
+    "next": "latest",
     "react": "19.0.0-rc-6230622a1a-20240610",
     "react-dom": "19.0.0-rc-6230622a1a-20240610"
   },