Add a gyp/gn variable for whether to use iLBC or not

webrtc/build/common.gypi

Index: webrtc/build/common.gypi
diff --git a/webrtc/build/common.gypi b/webrtc/build/common.gypi
index 9fa3ce31933f93e78bfd888a47591e291536b3e4..76545147a56073a96f285db47cfb5b64293b00b8 100644
--- a/webrtc/build/common.gypi
+++ b/webrtc/build/common.gypi
@@ -40,6 +40,9 @@
       'include_opus%': 1,
       'opus_dir%': '<(DEPTH)/third_party/opus',
 
+      # Include the iLBC audio codec?
+      'include_ilbc%': 0,

[hlundin-webrtc, 2016/01/12 16:15:41]

I'm not sure we want this to be default off. This does change the behavior for
non-chrome non-firefox integrations of WebRTC. We should probably announce that,
at the very least.

[kwiberg-webrtc, 2016/01/14 10:59:31]

I changed it to the same default as before. See patch set #3.

+
       # Enable to use the Mozilla internal settings.
       'build_with_mozilla%': 0,
     },
@@ -50,6 +53,7 @@
     'modules_java_gyp_path%': '<(modules_java_gyp_path)',
     'webrtc_vp8_dir%': '<(webrtc_vp8_dir)',
     'webrtc_vp9_dir%': '<(webrtc_vp9_dir)',
+    'include_ilbc%': '<(include_ilbc)',
     'include_opus%': '<(include_opus)',
     'rtc_relative_path%': 1,
     'external_libraries%': '0',