Honor $CC/$CC_host and friends in make generator.

test/compiler-override/compiler-global-settings.gyp.in

+# Copyright (c) 2012 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.
+
+{
+  # PYTHON and PWD are replaced by the test code before this
+  # gyp file runs
+  'make_global_settings': [
+    ['CC', '$PYTHON $PWD/my_cc.py FOO'],
+    ['CXX', '$PYTHON $PWD/my_cxx.py FOO'],
+    ['CC.host', '$PYTHON $PWD/my_cc.py BAR'],
+    ['CXX.host', '$PYTHON $PWD/my_cxx.py BAR'],
+
+    ['LD', '$PYTHON $PWD/my_ld.py FOO_LINK'],
+    ['LD.host', '$PYTHON $PWD/my_ld.py BAR_LINK'],
+    ['LINK', '$PYTHON $PWD/my_ld.py FOO_LINK'],
+    ['LINK.host', '$PYTHON $PWD/my_ld.py BAR_LINK'],
+  ],
+
+  # The above global settings should mean that
+  # that these targets are built using the fake
+  # toolchain above.
+  'targets': [
+    {
+      'toolset': '$TOOLSET',
+      'target_name': 'hello',
+      'type': 'executable',
+      'sources': [
+        'test.c',
+        'cxxtest.cc',
+      ],
+    },
+  ],
+}