Create a separate packages directory for running pub.

tools/list_pkg_directories.py

Index: tools/list_pkg_directories.py
diff --git a/tools/list_pkg_directories.py b/tools/list_pkg_directories.py
index f1b69f19623218478f3da1912f67df13f29e0ae6..d64604be17ad1e0005b20ae5a9b73bfc16a0ce6c 100644
--- a/tools/list_pkg_directories.py
+++ b/tools/list_pkg_directories.py
@@ -8,16 +8,29 @@ Used in pkg.gyp. Lists all of the directories in the directory passed in as an
 argument to this script which have a lib subdirectory.
 
 Usage:
-  python tools/list_pkg_directories.py directory_to_list
+  python tools/list_pkg_directories.py OPTIONS DIRECTORY
 '''
 
+import optparse
 import os
 import sys
 
+def get_options():
+  result = optparse.OptionParser()
+  result.add_option("--exclude",
+      help='A comma-separated list of directory names to exclude.')
+  return result.parse_args()
+
 def main(argv):
-  directory = argv[1]
-  paths = map(lambda x: x + '/lib', filter(lambda x: os.path.isdir(
-      os.path.join(directory, x)), os.listdir(directory)))
+  (options, args) = get_options()
+  directory = args[0]
+  exclude = options.exclude.split(',') if options.exclude else []
+
+  paths = [
+    path + '/lib' for path in os.listdir(directory)
+    if path not in exclude and os.path.isdir(os.path.join(directory, path))
+  ]
+
   for lib in filter(lambda x: os.path.exists(os.path.join(directory, x)),
       paths):
     print '%s/%s' % (directory, lib)