First crack at adding a GYP_GENERATOR for determining various things

test/analyzer/test.gyp

+# Copyright (c) 2014 Google Inc. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+  'variables': {
+    'test_variable%': 0,
+    'variable_path': 'subdir',
+   },
+  'targets': [
+    {
+      'target_name': 'exe',
+      'type': 'executable',
+      'dependencies': [
+        'subdir/subdir.gyp:foo',
+      ],
+      'sources': [
+        'foo.c',
+        '<(variable_path)/subdir_source2.c',
+      ],
+      'conditions': [
+        ['test_variable==1', {
+          'sources': [
+            'conditional_source.c',
+          ],
+        }],
+      ],
+      'actions': [
+        {
+          'action_name': 'action',
+          'inputs': [
+            '<(PRODUCT_DIR)/product_dir_input.c',
+            'action_input.c',
+          ],
+          'outputs': [
+            'action_output.c',
+          ],
+        },
+      ],
+      'rules': [
+        {
+          'rule_name': 'rule',
+          'extension': 'pdf',
+          'inputs': [
+            'rule_input.c',
+          ],
+          'outputs': [
+            'rule_output.pdf',
+          ],
+        },
+      ],
+    },
+  ],
+}