buildman: Put our local libraries first in the path

If patman is installed on the machine (e.g. in the standard dist-packages
directory), it will find libraries from there in preference to our local
libraries. Adjust the order of the path to ensure that local libraries are
found first.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/buildman.py b/tools/buildman/buildman.py
index d0afeda..607429d 100755
--- a/tools/buildman/buildman.py
+++ b/tools/buildman/buildman.py
@@ -15,7 +15,7 @@
 
 # Bring in the patman libraries
 our_path = os.path.dirname(os.path.realpath(__file__))
-sys.path.append(os.path.join(our_path, '../patman'))
+sys.path.insert(1, os.path.join(our_path, '../patman'))
 
 # Our modules
 import board