Move pdx_tool into system_ext

it is not a part of the system according to
generic_system.mk.

Bug: 173538619
Bug: 167689596
Test: presubmit
Signed-off-by: Roman Kiryanov <rkir@google.com>
Change-Id: I06d22d1086db330a4e56ae2f0939c4ef04683e82
diff --git a/libs/vr/libpdx_default_transport/Android.bp b/libs/vr/libpdx_default_transport/Android.bp
index 1ce9c99..b3534de 100644
--- a/libs/vr/libpdx_default_transport/Android.bp
+++ b/libs/vr/libpdx_default_transport/Android.bp
@@ -45,6 +45,7 @@
 
 cc_binary {
     name: "pdx_tool",
+    system_ext_specific: true,
     defaults: ["pdx_default_transport_compiler_defaults"],
     srcs: [
         "pdx_tool.cpp",