Disable libstdc++ debug mode on x64 for now.

TBR=mstarzinger@chromium.org

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24798 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

build/standalone.gypi

@@ -137,7 +137,7 @@
       'DebugBaseCommon': {
         'cflags': [ '-g', '-O0' ],
         'conditions': [
-          ['(v8_target_arch=="ia32" or v8_target_arch=="x64" or v8_target_arch=="x87") and \
+          ['(v8_target_arch=="ia32" or v8_target_arch=="x87") and \
             OS=="linux"', {
             'defines': [
               '_GLIBCXX_DEBUG'