win ninja: Refactor manifest generate and embed to be 1-pass

pylib/gyp/common.py

Index: pylib/gyp/common.py
diff --git a/pylib/gyp/common.py b/pylib/gyp/common.py
index b9d2abef02cd6aee3de95eec4347459537f082b7..f9c6c6f3a8ccbad11687127f2b1360389f10d1e8 100644
--- a/pylib/gyp/common.py
+++ b/pylib/gyp/common.py
@@ -391,6 +391,14 @@ def WriteOnDiff(filename):
   return Writer()
 
 
+def EnsureDirExists(path):
+  """Make sure the directory for |path| exists."""
+  try:
+    os.makedirs(os.path.dirname(path))
+  except OSError:
+    pass
+
+
 def GetFlavor(params):
   """Returns |params.flavor| if it's set, the system's default flavor else."""
   flavors = {