gpu/khronos_glcts_support: add support for GN builds

gpu/khronos_glcts_support/khronos_glcts_defaults.gypi

+# Copyright 2015 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.
+
+{
+  'target_defaults': {
+    'defines': [
+      'DEQP_TARGET_NAME="chrome-gpu-command-buffer"',
+      'DEQP_SUPPORT_GLES2=1',
+      'DEQP_SUPPORT_EGL=1',
+      'GTF_API=GTF_GLES20',
+    ],
+    'conditions': [
+      ['OS=="linux"', {
+        'defines': [
+          '_XOPEN_SOURCE=500',
+        ],
+        'cflags!': [
+          '-fno-exceptions',
+        ],
+        'cflags_cc!': [
+          '-fno-exceptions',
+        ],
+        'target_conditions': [
+          ['_type=="static_library"', {

[piman, 2015/10/28 22:45:38]

Why specific to static_library? 

[U. Artie Eoff, 2015/10/28 22:57:31]

Because all the khronos_glcts third_party code is compiled into static_libraries
and needs rtti to compile (due to use of dynamic_cast).  However, once we link
everything into any of the final executable(s), we need -fno-rtti, otherwise
native/main.cc fails to link due to "undefined reference to 'typeinfo for
base::MessageLoop'" since "base" was compiled with no-rtti.

Note that this section isn't new code... it was only cut and pasted from
khronos_glcts.gypi.

+            'cflags_cc!': [
+              '-fno-rtti',
+            ],
+          }],
+        ],
+      }],
+    ],
+  },
+}