Use --copy-out to generate .bp file.

* The original include command now works without
  local patch or post_update.sh.

Bug: 171659849
Test: make
Test: tools/external_updater/updater.sh update --refresh --keep-date rust/crates/protobuf
Change-Id: I973c7ac3dfa4f8233f8522b1ada678a9ef144f73
diff --git a/src/lib.rs b/src/lib.rs
index 4a346c8..8233e07 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -95,4 +95,4 @@
 #[cfg(never)]
 #[doc(hidden)]
 pub const VERSION_IDENT: &str = "";
-include!("../out/version.rs");  // ANDROID
+include!(concat!(env!("OUT_DIR"), "/version.rs"));