add rustc build flags reflection

Signed-off-by: Jason Volk <jason@zemos.net>

src/macros/rustc.rs

@@ -0,0 +1,27 @@
+use proc_macro::TokenStream;
+use quote::quote;
+
+pub(super) fn flags_capture(args: TokenStream) -> TokenStream {
+	let cargo_crate_name = std::env::var("CARGO_CRATE_NAME");
+	let crate_name = match cargo_crate_name.as_ref() {
+		Err(_) => return args,
+		Ok(crate_name) => crate_name.trim_start_matches("conduit_"),
+	};
+
+	let flag = std::env::args().collect::<Vec<_>>();
+	let ret = quote! {
+		#[conduit_core::ctor]
+		fn _set_rustc_flags() {
+			let flags = &[#( #flag ),*];
+			conduit_core::info::rustc::FLAGS.lock().expect("locked").insert(#crate_name, flags);
+		}
+
+		// static strings have to be yanked on module unload
+		#[conduit_core::dtor]
+		fn _unset_rustc_flags() {
+			conduit_core::info::rustc::FLAGS.lock().expect("locked").remove(#crate_name);
+		}
+	};
+
+	ret.into()
+}