build: fix compilation errors in utility scripts (#21488)

Fixes a few compilation errors in some utility scripts that haven't been caught by the CI.

(cherry picked from commit 64c3917)

Author: crisbeto

tools/dev-server/dev-server.ts

@@ -39,7 +39,7 @@ export class DevServer {
 
   /** Starts the server on the given port. */
   async start() {
-    return new Promise((resolve, reject) => {
+    return new Promise<void>((resolve, reject) => {
       this.server.init(this.options, (err) => {
         if (err) {
           reject(err);

tools/release/changelog.ts

@@ -69,7 +69,7 @@ export async function prependChangelogFromLatestTag(changelogPath: string, relea
   // actually prepend the new changelog to the existing one.
   const previousChangelogStream = createReadStream(changelogPath);
 
-  return new Promise((resolve, reject) => {
+  return new Promise<void>((resolve, reject) => {
     // Sequentially merge the changelog output and the previous changelog stream, so that
     // the new changelog section comes before the existing versions. Afterwards, pipe into the
     // changelog file, so that the changes are reflected on file system.

tools/release/release-output/check-package.ts

@@ -37,7 +37,7 @@ export function checkReleasePackage(
     releasesPath: string, packageName: string, expectedVersion: string): boolean {
   const packagePath = join(releasesPath, packageName);
   const failures = new Map() as PackageFailures;
-  const addFailure = (message, filePath?) => {
+  const addFailure = (message: string, filePath?: string) => {
     const filePaths = failures.get(message) || [];
     if (filePath) {
       filePaths.push(filePath);