No stage name for a single stage build.

git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@297444 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/zorg/buildbot/builders/UnifiedTreeBuilder.py b/zorg/buildbot/builders/UnifiedTreeBuilder.py
index c29f519..e5fca1d 100644
--- a/zorg/buildbot/builders/UnifiedTreeBuilder.py
+++ b/zorg/buildbot/builders/UnifiedTreeBuilder.py
@@ -107,6 +107,7 @@
     if stage_name:
         step_name = "cmake-configure-%s" % stage_name
     else:
+        stage_name = ""
         step_name = "cmake-configure"
 
     src_dir = LLVMBuildFactory.pathRelativeToBuild(f.llvm_srcdir, obj_dir)
@@ -133,6 +134,7 @@
     if stage_name:
         step_name = "%s-" % stage_name
     else:
+        stage_name = ""
         step_name = ""
 
     if obj_dir is None: