Performance improvements for "build-plugin" task

Summary:
Few improvements for "build-plugin" task which together with Sandcastle command changes (D26872427) helps to build all plugins in CI ~30% faster if most of them has not changed (which is usually the case):
1) compute package checksum in the same script to not call additional yarn scripts for each plugin
2) avoid packaging plugin if it's checksum has not changed since last release

Reviewed By: mweststrate

Differential Revision: D26872253

fbshipit-source-id: 968102d32a1550ea7503f1169f0ef2863296383f

desktop/pkg/src/utils/computePackageChecksum.ts

@@ -1,50 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- *
- * @format
- */
-
-import packlist from 'npm-packlist';
-import path from 'path';
-import crypto from 'crypto';
-import fs from 'fs-extra';
-
-export default async function computePackageChecksum(
-  dir: string,
-): Promise<string> {
-  const hash = crypto.createHash('sha1');
-  hash.setEncoding('hex');
-  const files = (await packlist({path: dir})).sort();
-  for (const file of files) {
-    // add hash of relative file path
-    hash.write(process.platform === 'win32' ? file.replace(/\\/g, '/') : file);
-
-    const filePath = path.resolve(dir, file);
-
-    if (file === 'package.json') {
-      // add hash of package.json with version set to "0.0.0" to avoid changing hash when only version changed
-      const packageJson = await fs.readJson(filePath);
-      if (packageJson.version) {
-        packageJson.version = '0.0.0';
-      }
-      hash.write(JSON.stringify(packageJson));
-    } else {
-      // add hash of file content
-      const stream = fs.createReadStream(filePath);
-      try {
-        stream.pipe(hash, {end: false});
-        await new Promise((resolve, reject) => {
-          stream.once('end', resolve);
-          stream.once('error', reject);
-        });
-      } finally {
-        stream.close();
-      }
-    }
-  }
-  hash.end();
-  return hash.read();
-}