Added more targets to .gn.

NOTRY=True

Review-Url: https://codereview.webrtc.org/2276933002
Cr-Commit-Position: refs/heads/master@{#13896}
diff --git a/.gn b/.gn
index 54eb15b..cc35c5f 100644
--- a/.gn
+++ b/.gn
@@ -26,7 +26,7 @@
   "//webrtc/modules/audio_coding:isac_test",
   "//webrtc/modules/audio_coding:webrtc_opus_fec_test",
   "//webrtc/modules/audio_device/*",
-  "//webrtc/modules/audio_mixer:audio_conference_mixer",
+  "//webrtc/modules/audio_mixer/*",
   "//webrtc/voice_engine:level_indicator",
 ]