Add chromecast_build gyp variable and add rules when the variable is set to 1.

build/linux/system.gyp

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'conditions': [
       ['sysroot!=""', {
         'pkg-config': '<(chroot_cmd) ./pkg-config-wrapper "<(sysroot)" "<(target_arch)"',
         # libgcrypt-config-wrapper invokes libgcrypt-config directly from the 
@@ skipping 1031 matching lines @@
             'ldflags': [
               '<!@(<(pkg-config) --libs-only-L --libs-only-other libudev)',
             ],
             'libraries': [
               '<!@(<(pkg-config) --libs-only-l libudev)',
             ],
           },
         }],
       ],
     },
+    {
+      'target_name': 'directfb',
+      'type': 'none',
+      'conditions': [
+        ['_toolset=="target"', {
+          'direct_dependent_settings': {
+            'cflags': [
+              '<!@(<(pkg-config) --cflags directfb)',
+            ],
+          },
+          'link_settings': {
+            'ldflags': [
+              '<!@(<(pkg-config) --libs-only-L --libs-only-other directfb)',
+            ],
+            'libraries': [
+              '<!@(<(pkg-config) --libs-only-l directfb)',
+            ],
+          },
+        }],
+      ],
+    },
   ],
 }