chore: Add command stdout to the error message if apksigner fails

lib/tools/apk-signing.js

@@ -279,7 +279,7 @@ apkSigningMethods.checkApkCert = async function checkApkCert (appPath, pkg, opts
       return false;
     }
     throw new Error(`Cannot verify the signature of '${appPath}'. ` +
-      `Original error: ${err.stderr || err.message}`);
+      `Original error: ${err.stderr || err.stdout || err.message}`);
   }
 };