IDL build: factor out global objects action into a GYP template

Source/bindings/bindings.gypi

Index: Source/bindings/bindings.gypi
diff --git a/Source/bindings/bindings.gypi b/Source/bindings/bindings.gypi
index 0b249244a565300fc67b0c4dc0b0ff8d48c774f9..354b185c08323da1d909833bdbf1b9a205454e17 100644
--- a/Source/bindings/bindings.gypi
+++ b/Source/bindings/bindings.gypi
@@ -11,19 +11,5 @@
         'bindings_unittest_files': [
             '<@(bindings_v8_unittest_files)',
         ],
-        'conditions': [
-            # The bindings generator can skip writing generated files if they
-            # are identical to the already existing file, which avoids
-            # recompilation.  However, a dependency (earlier build step) having
-            # a newer timestamp than an output (later build step) confuses some
-            # build systems, so only use this on ninja, which explicitly
-            # supports this use case (gyp turns all actions into ninja restat
-            # rules).
-            ['"<(GENERATOR)"=="ninja"', {
-              'write_file_only_if_changed': '1',
-            }, {
-              'write_file_only_if_changed': '0',
-            }],
-        ],
     },
 }