ninja windows: support precompiled headers

pylib/gyp/xcode_emulation.py

Index: pylib/gyp/xcode_emulation.py
diff --git a/pylib/gyp/xcode_emulation.py b/pylib/gyp/xcode_emulation.py
index 9ed98d5fab53fc44def0cb0474057bdd948ec9a1..7fd795034ec5354d84696ecd52bb1728fa412264 100644
--- a/pylib/gyp/xcode_emulation.py
+++ b/pylib/gyp/xcode_emulation.py
@@ -752,17 +752,17 @@ class MacPrefixHeader(object):
         result.append((source, obj, self._Gch(lang)))
     return result
 
-  def GetGchBuildCommands(self):
-    """Returns [(path_to_gch, language_flag, language, header)].
+  def GetPchBuildCommands(self):
+    """Returns [(path_to_gch, language_flag, language, header, extra_vars)].
     |path_to_gch| and |header| are relative to the build directory.
     """
     if not self.header or not self.compile_headers:
       return []
     return [
-      (self._Gch('c'), '-x c-header', 'c', self.header),
-      (self._Gch('cc'), '-x c++-header', 'cc', self.header),
-      (self._Gch('m'), '-x objective-c-header', 'm', self.header),
-      (self._Gch('mm'), '-x objective-c++-header', 'mm', self.header),
+      (self._Gch('c'), '-x c-header', 'c', self.header, []),
+      (self._Gch('cc'), '-x c++-header', 'cc', self.header, []),
+      (self._Gch('m'), '-x objective-c-header', 'm', self.header, []),
+      (self._Gch('mm'), '-x objective-c++-header', 'mm', self.header, []),
     ]