streamline build scripts
diff --git a/releng.control/checkout.xml b/releng.control/checkout.xml
index 1bd00f2..71dbf0a 100644
--- a/releng.control/checkout.xml
+++ b/releng.control/checkout.xml
@@ -289,6 +289,7 @@
             is fetched to control the rest of the build -->
         <property
             file="${codir}/${env.RELENG}/maps/build.cfg" />
+        <fail unless="builderVersion" message="Could not get builderVersion. Probably could not checkout build.cfg" />
         <delete
             dir="${codir}/${env.RELENG_BUILDER}"
             failonerror="false" />