APM: Add build flag to allow building WebRTC without APM

This CL adds a build flag to allow building the non-test parts
of WebRTC without the audio processing module.
The CL also ensures that the WebRTC code correctly handles
the case when no APM is available.

Bug: webrtc:5298
Change-Id: I5c8b5d1f7115e5cce2af4c2b5ff701fa1c54e49e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/171509
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31133}
diff --git a/modules/audio_processing/test/debug_dump_replayer.cc b/modules/audio_processing/test/debug_dump_replayer.cc
index 26ca429..b8cccd1 100644
--- a/modules/audio_processing/test/debug_dump_replayer.cc
+++ b/modules/audio_processing/test/debug_dump_replayer.cc
@@ -10,6 +10,7 @@
 
 #include "modules/audio_processing/test/debug_dump_replayer.h"
 
+#include "modules/audio_processing/test/audio_processing_builder_for_testing.h"
 #include "modules/audio_processing/test/protobuf_utils.h"
 #include "modules/audio_processing/test/runtime_setting_util.h"
 #include "rtc_base/checks.h"
@@ -185,7 +186,7 @@
   // We only create APM once, since changes on these fields should not
   // happen in current implementation.
   if (!apm_.get()) {
-    apm_.reset(AudioProcessingBuilder().Create(config));
+    apm_.reset(AudioProcessingBuilderForTesting().Create(config));
   }
 }