Allow factory server to run

* Don't import builder unless a build is requested.

BUG=chrome-os-partner:4941
TEST=run outside chroot

Change-Id: Id42f2456e21403af8edf0f765c4a3865e543fd26
Reviewed-on: http://gerrit.chromium.org/gerrit/5337
Tested-by: Nick Sanders <nsanders@chromium.org>
Reviewed-by: David James <davidjames@chromium.org>
diff --git a/devserver.py b/devserver.py
index 505ea5a..a17f55c 100755
--- a/devserver.py
+++ b/devserver.py
@@ -13,7 +13,6 @@
 import sys
 
 import autoupdate
-import builder
 
 CACHED_ENTRIES = 12
 
@@ -88,10 +87,13 @@
   """
 
   def __init__(self):
-    self._builder = builder.Builder()
+    self._builder = None
 
   def build(self, board, pkg, **kwargs):
     """Builds the package specified."""
+    import builder
+    if self._builder is None:
+      self._builder = builder.Builder()
     return self._builder.Build(board, pkg, kwargs)
 
   def index(self):