Fix generators to make sure changes to rule inputs trigger correct rebuilds....

test/rules-rebuild/src/same_target.gyp

Index: test/rules-rebuild/src/same_target.gyp
===================================================================
--- test/rules-rebuild/src/same_target.gyp	(revision 0)
+++ test/rules-rebuild/src/same_target.gyp	(revision 0)
@@ -0,0 +1,32 @@
+{
+  'targets': [
+    {
+      'target_name': 'program',
+      'type': 'executable',
+      'msvs_cygwin_shell': 0,
+      'sources': [
+        'main.c',
+        'prog1.in',
+        'prog2.in',
+      ],
+      'rules': [
+        {
+          'rule_name': 'make_sources',
+          'extension': 'in',
+          'msvs_external_rule': 1,
+          'inputs': [
+            'make-sources.py',
+          ],
+          'outputs': [
+            '<(INTERMEDIATE_DIR)/<(RULE_INPUT_ROOT).c',
+            '<(INTERMEDIATE_DIR)/<(RULE_INPUT_ROOT).h',
+          ],
+          'action': [
+            'python', '<(_inputs)', '<(RULE_INPUT_NAME)', '<@(_outputs)',
+          ],
+          'process_outputs_as_sources': 1,
+        },
+      ],
+    },
+  ],
+}