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/api/audio/BUILD.gn b/api/audio/BUILD.gn
index 73973bd..ab9bae8 100644
--- a/api/audio/BUILD.gn
+++ b/api/audio/BUILD.gn
@@ -53,6 +53,7 @@
   deps = [
     ":aec3_config",
     ":echo_control",
+    "../../modules/audio_processing/aec3",
   ]
 }