Thread Crubit feature flags into the IR and `src_code_gen.rs`.
This does not yet use it for anything except to display which features are enabled, as a comment at the top of the file.
PiperOrigin-RevId: 513385210
diff --git a/rs_bindings_from_cc/test/golden/friend_functions_rs_api.rs b/rs_bindings_from_cc/test/golden/friend_functions_rs_api.rs
index 1d9a6d0..20101a1 100644
--- a/rs_bindings_from_cc/test/golden/friend_functions_rs_api.rs
+++ b/rs_bindings_from_cc/test/golden/friend_functions_rs_api.rs
@@ -4,6 +4,7 @@
// Automatically @generated Rust bindings for the following C++ target:
// //rs_bindings_from_cc/test/golden:friend_functions_cc
+// Features: experimental, supported
#![rustfmt::skip]
#![feature(custom_inner_attributes)]
