[tests] Fix tarball lookup with sha contains 0 (#8552)

This PR fixes an issue when the sha begins with `0` and causes [an error](https://vercel.com/vercel/vercel/EP7fVcXKsoodzWRy3fwG8AoeQcs6) when looking up the tarball:

> Error: ENOENT: no such file or directory, 
> copyfile '/vercel/path0/packages/build-utils/vercel-build-utils-v5.4.2-0251253.tgz' 
>  -> '/vercel/path0/public/tarballs/@vercel/build-utils.tgz'

The fix is to no longer rely on the exact tarball name because we can't guarantee the name from `yarn pack` and instead rely on a pattern for the tarball name.

api/_lib/script/build.ts

@@ -1,6 +1,5 @@
 import fs from 'fs/promises';
 import { join, dirname } from 'path';
-import execa from 'execa';
 import { getExampleList } from '../examples/example-list';
 import { mapOldToNew } from '../examples/map-old-to-new';
 
@@ -47,10 +46,6 @@ async function main() {
     JSON.stringify([...existingExamples, ...oldExamples])
   );
 
-  const { stdout: sha } = await execa('git', ['rev-parse', '--short', 'HEAD'], {
-    cwd: repoRoot,
-  });
-
   const tarballsDir = join(pubDir, 'tarballs');
   const packagesDir = join(repoRoot, 'packages');
   const packages = await fs.readdir(packagesDir);
@@ -61,12 +56,21 @@ async function main() {
       'utf-8'
     );
     const packageJson = JSON.parse(packageJsonRaw);
-    const tarballName = `${packageJson.name
-      .replace('@', '')
-      .replace('/', '-')}-v${packageJson.version}-${sha.trim()}.tgz`;
+    const files = await fs.readdir(fullDir);
+    const tarballName = files.find(f => /^vercel-.+\.tgz$/.test(f));
+    if (!tarballName) {
+      throw new Error(
+        `Expected vercel-*.tgz in ${fullDir} but found ${JSON.stringify(
+          files,
+          null,
+          2
+        )}`
+      );
+    }
+    const srcTarballPath = join(fullDir, tarballName);
     const destTarballPath = join(tarballsDir, `${packageJson.name}.tgz`);
     await fs.mkdir(dirname(destTarballPath), { recursive: true });
-    await fs.copyFile(join(fullDir, tarballName), destTarballPath);
+    await fs.copyFile(srcTarballPath, destTarballPath);
   }
 
   console.log('Completed building static frontend.');