Don't rely on `touch' being available (windows ninja)

pylib/gyp/generator/ninja.py

Index: pylib/gyp/generator/ninja.py
===================================================================
--- pylib/gyp/generator/ninja.py	(revision 1226)
+++ pylib/gyp/generator/ninja.py	(working copy)
@@ -1194,11 +1194,11 @@
       description='PACKAGE FRAMEWORK $out, POSTBUILDS',
       command='$mac_tool package-framework $out $version$postbuilds '
               '&& touch $out')
-  master_ninja.rule(
-    'stamp',
-    description='STAMP $out',
-    command='${postbuilds}touch $out')
   if flavor == 'win':
+    master_ninja.rule(
+      'stamp',
+      description='STAMP $out',
+      command='cmd /c copy /y nul $out>nul')
     # TODO(scottmg): Copy fallback?
     master_ninja.rule(
       'copy',
@@ -1206,6 +1206,10 @@
       command='cmd /c mklink /h $out $in >nul || mklink /h /j $out $in >nul')
   else:
     master_ninja.rule(
+      'stamp',
+      description='STAMP $out',
+      command='${postbuilds}touch $out')
+    master_ninja.rule(
       'copy',
       description='COPY $in $out',
       command='ln -f $in $out 2>/dev/null || (rm -rf $out && cp -af $in $out)')