Circle CI: (FIX) Build release package outside of publish-npm.js

Summary:
The version of npm available in Circle CI is 6.x, which does not support the `--pack-destination` argument. As a result, `npm pack --pack-destination build` was interpreted as a request to package the 'build' directory for distribution.

Since we need to make sure the output of `npm pack` is consumed by Circle CI's `store_artifacts` directive, we move the commitlies release packing logic to the Circle CI job config itself as to reduce coupling between `publish-npm.js` and the Circle CI config.

Changelog: [Internal]

Reviewed By: sota000

Differential Revision: D31183635

fbshipit-source-id: f0e0baae4ae31941dbb78dd1fec689f0f3398b52

.circleci/config.yml

@@ -738,8 +738,14 @@ jobs:
           condition:
             equal: [ --dry-run, << parameters.publish_npm_args >> ]
           steps:
+            - run:
+                name: Build release package as a job artifact
+                command: |
+                  mkdir -p build
+                  FILENAME=$(npm pack)
+                  mv $FILENAME build/
             - store_artifacts:
-                path: ~/react-native/react-native-1000.0.0.tgz
+                path: ~/react-native/build/
                 destination: build
 
   # -------------------------

scripts/publish-npm.js

@@ -163,30 +163,24 @@ artifacts.forEach(name => {
 
 if (dryRunBuild) {
   echo('Skipping `npm publish` because --dry-run is set.');
-  if (exec('mkdir -p build && npm pack --pack-destination build').code) {
-    echo('Failed to build release package.');
-    exit(1);
-  } else {
-    echo('The release was built successfully.');
-    exit(0);
-  }
+  exit(0);
+}
+
+// if version contains -rc, tag as prerelease
+const tagFlag = nightlyBuild
+  ? '--tag nightly'
+  : releaseVersion.indexOf('-rc') === -1
+  ? ''
+  : '--tag next';
+
+// use otp from envvars if available
+const otpFlag = otp ? `--otp ${otp}` : '';
+
+if (exec(`npm publish ${tagFlag} ${otpFlag}`).code) {
+  echo('Failed to publish package to npm');
+  exit(1);
 } else {
-  // if version contains -rc, tag as prerelease
-  const tagFlag = nightlyBuild
-    ? '--tag nightly'
-    : releaseVersion.indexOf('-rc') === -1
-    ? ''
-    : '--tag next';
-
-  // use otp from envvars if available
-  const otpFlag = otp ? `--otp ${otp}` : '';
-
-  if (exec(`npm publish ${tagFlag} ${otpFlag}`).code) {
-    echo('Failed to publish package to npm');
-    exit(1);
-  } else {
-    echo(`Published to npm ${releaseVersion}`);
-    exit(0);
-  }
+  echo(`Published to npm ${releaseVersion}`);
+  exit(0);
 }
 /*eslint-enable no-undef */