Make sure we do not have stale entries inside build-dir/packages

dart/tools/make_links.py

Index: dart/tools/make_links.py
diff --git a/dart/tools/make_links.py b/dart/tools/make_links.py
index 66f94e6b134d2a6b24f0c7ef1eeb51a878ccb025..6c08144d2f1b4ea1b45b2970d9547877a55a72ff 100644
--- a/dart/tools/make_links.py
+++ b/dart/tools/make_links.py
@@ -10,12 +10,16 @@ For each SOURCE in SOURCES create a link from SOURCE to TARGET.  If a
 SOURCE ends with .../lib, the lib suffix is ignored when determining
 the name of the target link.
 
+Before creating any links, the old entries of the TARGET directory will be
+removed.
+
 Usage:
   python tools/make_links.py OPTIONS TARGET SOURCES...
 '''
 
 import optparse
 import os
+import shutil
 import subprocess
 import sys
 import utils
@@ -53,13 +57,18 @@ def create_timestamp_file(options):
     if not os.path.exists(dir_name):
       os.mkdir(dir_name)
     open(options.timestamp_file, 'w').close()
-  
+
 
 def main(argv):
   (options, args) = get_options()
   target = os.path.relpath(args[0])
-  if not os.path.exists(target):
-    os.makedirs(target)
+  if os.path.exists(target):
+    # Remove the packages directory if it already exists.
+    # This is necessary, otherwise we can end up having links in there
+    # pointing to directories which no longer exist (on incremental builds).
+    print 'Removing %s' % target
+    shutil.rmtree(target)
+  os.makedirs(target)
   for source in args[1:]:
     # Assume the source directory is named ".../NAME/lib".
     (name, lib) = os.path.split(source)