Teach ninja to handle output directories outside the source dir.

pylib/gyp/common.py

Index: pylib/gyp/common.py
===================================================================
--- pylib/gyp/common.py	(revision 1537)
+++ pylib/gyp/common.py	(working copy)
@@ -128,8 +128,8 @@
   # relative_to.
 
   # Convert to absolute (and therefore normalized paths).

[Nico, 2012/12/21 22:52:08]

Is the comment now out of date?

-  path = os.path.abspath(path)
-  relative_to = os.path.abspath(relative_to)
+  path = os.path.realpath(path)
+  relative_to = os.path.realpath(relative_to)
 
   # Split the paths into components.
   path_split = path.split(os.path.sep)
@@ -151,6 +151,20 @@
   return os.path.join(*relative_split)
 
 
+@memoize
+def InvertRelativePath(path, toplevel_dir=None):
+  """Given a path like foo/bar that is relative to toplevel_dir, return
+  the inverse relative path back to the toplevel_dir.
+
+  E.g. os.path.normpath(os.path.join(path, InvertRelativePath(path)))
+  should always produce the empty string, unless the path contains symlinks.
+  """
+  if not path:
+    return path
+  toplevel_dir = '.' if toplevel_dir is None else toplevel_dir
+  return RelativePath(toplevel_dir, os.path.join(toplevel_dir, path))
+
+
 def FixIfRelativePath(path, relative_to):
   # Like RelativePath but returns |path| unchanged if it is absolute.
   if os.path.isabs(path):