Separate build targets for aec3 and aec3_unittests

Bug: webrtc:8844
Change-Id: Id6a98eae19aaedc87c3f402a004f58f0290d5c28
Reviewed-on: https://webrtc-review.googlesource.com/56580
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Reviewed-by: Alex Loiko <aleloi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22173}
diff --git a/modules/BUILD.gn b/modules/BUILD.gn
index c4010a2..aa76b0f 100644
--- a/modules/BUILD.gn
+++ b/modules/BUILD.gn
@@ -258,6 +258,7 @@
       "audio_device:audio_device_unittests",
       "audio_mixer:audio_mixer_unittests",
       "audio_processing:audio_processing_unittests",
+      "audio_processing/aec3:aec3_unittests",
       "bitrate_controller:bitrate_controller_unittests",
       "congestion_controller:congestion_controller_unittests",
       "pacing:pacing_unittests",