add prepack script

Author: lobsterkatie

packages/utils/scripts/prepack.ts

@@ -0,0 +1,28 @@
+/* eslint-disable no-console */
+
+// DO NOT RUN this script yourself!
+// This is invoked from the main `prepack.ts` script in `sentry-javascript/scripts/prepack.ts`.
+
+import * as fs from 'fs';
+import * as fse from 'fs-extra';
+import * as path from 'path';
+
+export function prepack(buildDir: string): boolean {
+  // copy package-specific assets to build dir
+  const assetPath = path.resolve('jsPolyfills');
+  const destinationPath = path.resolve(buildDir, 'jsPolyfills');
+  try {
+    if (!fs.existsSync(assetPath)) {
+      console.error(
+        "\nERROR: Missing 'packages/utils/jsPolyfills' directory. Please run `yarn build` in the `utils` package before running this script again.",
+      );
+      return false;
+    }
+    console.log(`Copying jsPolyfills to ${path.relative('../..', destinationPath)}.`);
+    fse.copySync(assetPath, destinationPath);
+  } catch (error) {
+    console.error(`\nERROR: Error while copying jsPolyfills to ${path.relative('../..', destinationPath)}:\n${error}`);
+    return false;
+  }
+  return true;
+}