Rename targets to use lower case format.

It makes writing a build script for merging libraries
across architectures easier. See talk/build/build_ios_libs.sh.

BUG=
R=andrew@webrtc.org, kjellander@webrtc.org

Review URL: https://codereview.webrtc.org/1171793002.

Cr-Commit-Position: refs/heads/master@{#9412}

webrtc/modules/audio_coding/codecs/cng/cng.gypi

@@ -9,7 +9,7 @@
 {
   'targets': [
     {
-      'target_name': 'CNG',
+      'target_name': 'cng',
       'type': 'static_library',
       'dependencies': [
         '<(webrtc_root)/common_audio/common_audio.gyp:common_audio',