Included variable default for d8.gyp.

TEST=build/gyp_v8 --generator-output=testbuild/

Review URL: http://codereview.chromium.org/7384006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8659 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/d8.gyp

@@ -26,6 +26,9 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 {
+  'variables': {
+    'console%': '',
+  },
   'targets': [
     {
       'target_name': 'd8',