Default to empty string for build sha, if it's not present from any other sources

Author: brianseeders

src/dev/build/lib/version_info.ts

@@ -30,7 +30,7 @@ export async function getVersionInfo({ isRelease, versionQualifier, pkg }: Optio
 
   const buildSha = fs.existsSync('.git')
     ? (await execa('git', ['rev-parse', 'HEAD'])).stdout
-    : process.env.GIT_COMMIT || process.env.BUILDKITE_COMMIT;
+    : process.env.GIT_COMMIT || process.env.BUILDKITE_COMMIT || '';
 
   return {
     buildSha,