chore(build): Ensure experimental builds exists on windows (#20933)

* chore(build): Throw if `rsync` fails

* did not get cwrsync to work

scripts/rollup/build-all-release-channels.js

@@ -64,7 +64,7 @@ if (process.env.CIRCLE_NODE_TOTAL) {
  // will have already removed conflicting files.
  //
  // In CI, merging is handled automatically by CircleCI's workspace feature.
- spawnSync('rsync', ['-ar', experimentalDir + '/', stableDir + '/']);
+ mergeDirsSync(experimentalDir + '/', stableDir + '/');
 
  // Now restore the combined directory back to its original name
  // TODO: Currently storing artifacts as `./build2` so that it doesn't conflict
@@ -186,3 +186,23 @@ function updateTheReactVersionThatDevToolsReads(version) {
  `export default '${version}';\n`
  );
 }
+
+/**
+ * cross-platform alternative to `rsync -ar`
+ * @param {string} source
+ * @param {string} destination
+ */
+function mergeDirsSync(source, destination) {
+ for (const sourceFileBaseName of fs.readdirSync(source)) {
+ const sourceFileName = path.join(source, sourceFileBaseName);
+ const targetFileName = path.join(destination, sourceFileBaseName);
+
+ const sourceFile = fs.statSync(sourceFileName);
+ if (sourceFile.isDirectory()) {
+ fse.ensureDirSync(targetFileName);
+ mergeDirsSync(sourceFileName, targetFileName);
+ } else {
+ fs.copyFileSync(sourceFileName, targetFileName);
+ }
+ }
+}