Add sound_trigger_manager_api flag.

The flag is used to control adding SoundTriggerManager apis
to SystemApi.

Bug: 339267254, 340549850
Test: Build image for Pixel Watch devices.

Change-Id: Ib30ed4dcedfcd09ce65ef7770829df0ebd0f3cb6
diff --git a/media/audio/aconfig/soundtrigger.aconfig b/media/audio/aconfig/soundtrigger.aconfig
index e61e6a3..fe5481d 100644
--- a/media/audio/aconfig/soundtrigger.aconfig
+++ b/media/audio/aconfig/soundtrigger.aconfig
@@ -12,3 +12,11 @@
     description: "Feature flag for adding GenericSoundModel to SystemApi"
     bug: "339267254"
 }
+
+flag {
+    name: "sound_trigger_manager_api"
+    is_exported: true
+    namespace: "soundtrigger"
+    description: "Feature flag for adding SoundTriggerManager API to SystemApi"
+    bug: "339267254"
+}