add gyp define to enable svn version check. defaults to off so tests built…

add gyp define to enable svn version check.  defaults to off so tests built outside of svn will build/run with a warning but not error.
BUG=356
TESTED=set GYP_DEFINES=target_arch=ia32 libyuv_disable_jpeg=1 libyuv_enable_svn=1
R=thorcarpenter@google.com

Review URL: https://webrtc-codereview.appspot.com/17329004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1075 16f28f9a-4ce2-e073-06de-1de4eb20be90

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 1074
+Version: 1075
 License: BSD
 License File: LICENSE
 

include/libyuv/version.h

@@ -11,6 +11,6 @@
 #ifndef INCLUDE_LIBYUV_VERSION_H_  // NOLINT
 #define INCLUDE_LIBYUV_VERSION_H_
 
-#define LIBYUV_VERSION 1074
+#define LIBYUV_VERSION 1075
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_  NOLINT

libyuv_test.gyp

@@ -9,6 +9,7 @@
 {
   'variables': {
     'libyuv_disable_jpeg%': 0,
+    'libyuv_enable_svn%': 0,
   },
   'targets': [
     {
@@ -21,7 +22,6 @@
         'testing/gtest.gyp:gtest_main',
       ],
       'defines': [
-        'LIBYUV_SVNREVISION="<!(svnversion -n)"',
         # Enable the following 3 macros to turn off assembly for specified CPU.
         # 'LIBYUV_DISABLE_X86',
         # 'LIBYUV_DISABLE_NEON',
@@ -49,6 +49,11 @@
         'unit_test/version_test.cc',
       ],
       'conditions': [
+        [ 'libyuv_enable_svn == 1', {
+          'defines': [
+            'LIBYUV_SVNREVISION="<!(svnversion -n)"',
+          ],
+        }],
         ['OS=="linux"', {
           'cflags': [
             '-fexceptions',

unit_test/version_test.cc

@@ -36,6 +36,8 @@ TEST_F(libyuvTest, TestVersion) {
   if (LIBYUV_VERSION != svn_revision) {
     printf("WARNING - Versions do not match.\n");
   }
+#else
+  printf("WARNING - SVN Version unavailable.  Test not run.\n");
 #endif
 }