build: add missing import for Lattice Diamond

sbourdeauducq · sbourdeauducq · commit 5e45b6ced6fe · 2015-09-29T15:44:57.000+08:00
diff --git a/migen/build/lattice/diamond.py b/migen/build/lattice/diamond.py
@@ -2,6 +2,7 @@
 # License: BSD
 
 import os
+import sys
 import subprocess
 import shutil
 
