Show build config in dumpsys SurfaceFlinger

This adds a line to the "dumpsys SurfaceFlinger" output that shows
build-time configuration values.

Example:
 Build configuration: [sf HAS_CONTEXT_PRIORITY] [libui] \
  [libgui USE_FENCE_SYNC]

Bug 7206633

Change-Id: Ibe1856b459d34a4be6ee83a4ebfd2807e6cc68a0
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index c9877b2..0a019ce 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -382,6 +382,7 @@
         String8& result, char* buffer, size_t SIZE) const;
     void dumpAllLocked(String8& result, char* buffer, size_t SIZE) const;
     bool startDdmConnection();
+    static void appendSfConfigString(String8& result);
 
     /* ------------------------------------------------------------------------
      * Attributes