.arg(sysroot)
.env(bootstrap::util::dylib_path_var(),
env::join_paths(&dylib_path).unwrap());
+
+ // Pass the `rustbuild` feature flag to crates which rustbuild is
+ // building. See the comment in bootstrap/lib.rs where this env var is
+ // set for more details.
+ if env::var_os("RUSTBUILD_UNSTABLE").is_some() {
+ cmd.arg("--cfg").arg("rustbuild");
+ }
+
std::process::exit(match cmd.status() {
Ok(s) => s.code().unwrap_or(1),
Err(e) => panic!("\n\nfailed to run {:?}: {}\n\n", cmd, e),