Add initial support for color output in the build system

lib/naclports/__main__.py

Index: lib/naclports/__main__.py
diff --git a/lib/naclports/__main__.py b/lib/naclports/__main__.py
index c3af29f1ad246ac29f18081750d559fa69619daf..828e3c0f9732c0491dfc0e4109aef0ed6498e2b1 100644
--- a/lib/naclports/__main__.py
+++ b/lib/naclports/__main__.py
@@ -275,10 +275,10 @@ def main(args):
   try:
     run_main(args)
   except KeyboardInterrupt:
-    sys.stderr.write('naclports: interrupted\n')
+    sys.stderr.write('naclports: %s\n' % util.Color('interrupted', 'red'))
     return 1
   except error.Error as e:
-    sys.stderr.write('naclports: %s\n' % e)
+    sys.stderr.write('naclports: %s\n' % util.Color(str(e), 'red'))
     return 1
 
   return 0