Bug 1496359 - Don't set _GLIBCXX_DEBUG in webrtc.org build config; r=ng

This define is not set in the current gn generated json and moz.build files.
If I rerun gn, this define ends up being set, and the build will fail with
a variety of link time errors.

My guess is that enable_iterator_debugging was not set when I last ran gn for
x64 Linux, and that it was subsequently enabled without regenerating the gn
files and noticing that it causes problems.

Differential Revision: https://phabricator.services.mozilla.com/D27367

--HG--
extra : moz-landing-system : lando

media/webrtc/trunk/webrtc/build/config/BUILD.gn

@@ -176,7 +176,7 @@ config("debug") {
     # Enable libstdc++ debugging facilities to help catch problems early, see
     # http://crbug.com/65151 .
     # TODO(phajdan.jr): Should we enable this for all of POSIX?
-    defines += [ "_GLIBCXX_DEBUG=1" ]
+    #defines += [ "_GLIBCXX_DEBUG=1" ]
   }
 }