Switch to generating private-code

This marks the generated Wayland symbols so they are not exported if the
static library built here is subsequently used by a shared library or
equivalent. For most normal uses this is desired, since those symbols
would not normally be part of that shared libraries public interface.

Bug: None
Test: m
Change-Id: I41c9e3c7ffdc73b403258b5560d7997fd4369779
diff --git a/gpu_display/Android.bp b/gpu_display/Android.bp
index 956eb94..4da12aa 100644
--- a/gpu_display/Android.bp
+++ b/gpu_display/Android.bp
@@ -35,7 +35,7 @@
 
 wayland_protocol_codegen {
     name: "gpu_display_protocol_sources",
-    cmd: "$(location wayland_scanner) code < $(in) > $(out)",
+    cmd: "$(location wayland_scanner) private-code < $(in) > $(out)",
     suffix: ".c",
     srcs: [
         "protocol/aura-shell.xml",