Build: use content hash for facebook-react-native build (#27577)

Similar to #26734, this switches the RN builds for Meta to a content
hash instead of git commit number to make the builds reproducible and
avoid creating sync commits if the bundled content didn't change.

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

@@ -8,6 +8,7 @@ const fse = require('fs-extra');
 const {spawnSync} = require('child_process');
 const path = require('path');
 const tmp = require('tmp');
+const glob = require('glob');
 
 const {
   ReactVersion,
@@ -235,19 +236,28 @@ function processExperimental(buildDir, version) {
     );
   }
 
-  if (fs.existsSync(buildDir + '/facebook-www')) {
-    const hash = crypto.createHash('sha1');
-    for (const fileName of fs.readdirSync(buildDir + '/facebook-www').sort()) {
-      const filePath = buildDir + '/facebook-www/' + fileName;
+  const facebookWwwDir = path.join(buildDir, 'facebook-www');
+  if (fs.existsSync(facebookWwwDir)) {
+    for (const fileName of fs.readdirSync(facebookWwwDir).sort()) {
+      const filePath = path.join(facebookWwwDir, fileName);
       const stats = fs.statSync(filePath);
       if (!stats.isDirectory()) {
-        hash.update(fs.readFileSync(filePath));
         fs.renameSync(filePath, filePath.replace('.js', '.modern.js'));
       }
     }
+    const contentHash = hashJSFilesInDirectory(facebookWwwDir);
     updatePlaceholderReactVersionInCompiledArtifacts(
-      buildDir + '/facebook-www',
-      ReactVersion + '-www-modern-' + hash.digest('hex').slice(0, 8)
+      facebookWwwDir,
+      ReactVersion + '-www-modern-' + contentHash
+    );
+  }
+
+  const facebookReactNativeDir = path.join(buildDir, 'facebook-react-native');
+  if (fs.existsSync(facebookReactNativeDir)) {
+    const contentHash = hashJSFilesInDirectory(facebookReactNativeDir);
+    updatePlaceholderReactVersionInCompiledArtifacts(
+      facebookReactNativeDir,
+      ReactVersion + '-react-native-' + contentHash
     );
   }
 
@@ -346,6 +356,14 @@ function updatePackageVersions(
   }
 }
 
+function hashJSFilesInDirectory(directory) {
+  const hash = crypto.createHash('sha1');
+  for (const filePath of glob.sync(directory + '/**/*.js').sort()) {
+    hash.update(fs.readFileSync(filePath));
+  }
+  return hash.digest('hex').slice(0, 8);
+}
+
 function updatePlaceholderReactVersionInCompiledArtifacts(
   artifactsDirectory,
   newVersion