Move AudioGain to libaudiofoundation.

1. Create folder for libaudiofoudation.
2. Move AudioGain to libaudiofoudation. The goal is to make AudioGain
be able to use in binder call and be vendor-available later.

Bug: 135621476
Test: make, CTS for AudioTrack, AudioRecord, AudioManagerTest
Change-Id: Ibf16ad9cb7f2ac657a02632ccbe4f934b5a12731
diff --git a/services/audiopolicy/engineconfigurable/Android.bp b/services/audiopolicy/engineconfigurable/Android.bp
index c27dc88..8f522f0 100644
--- a/services/audiopolicy/engineconfigurable/Android.bp
+++ b/services/audiopolicy/engineconfigurable/Android.bp
@@ -33,6 +33,7 @@
 
     ],
     shared_libs: [
+        "libaudiofoundation",
         "liblog",
         "libcutils",
         "libutils",