add libsurfaceflinger_ddmconnection for PDK build

- the library is dlopened from libsurfaceflinger
- the library built only when libnativehelper exists

Bug: 7089510
Change-Id: Ib3ea1029d7e8f6e055f4b759d0bf68f5123fa8a1
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 50fef00..9db6b2d 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -388,6 +388,7 @@
     void clearStatsLocked(const Vector<String16>& args, size_t& index,
         String8& result, char* buffer, size_t SIZE) const;
     void dumpAllLocked(String8& result, char* buffer, size_t SIZE) const;
+    bool startDdmConnection();
 
     /* ------------------------------------------------------------------------
      * Attributes