Add stubs to libjnigraphics

This is okay because libjnigraphics is an NDK library. When used by an
APEX, it needs to be loaded from the system, not bundlend in APEX.

Bug: n/a
Test: TH
Change-Id: I98851ea9fbc9f1779d628cc98875ee5310a1a478
diff --git a/native/graphics/jni/Android.bp b/native/graphics/jni/Android.bp
index 10c570b..866206c 100644
--- a/native/graphics/jni/Android.bp
+++ b/native/graphics/jni/Android.bp
@@ -72,6 +72,9 @@
             ],
         },
     },
+    stubs: {
+        symbol_file: "libjnigraphics.map.txt",
+    },
 }
 
 // The headers module is in frameworks/native/Android.bp.