RPM build fix (reverted CI changes which will need to be un-reverted or made conditional) and vendor Rust dependencies to make builds much faster in any CI system.

zeroidc/vendor/syn/tests/regression.rs

@@ -0,0 +1,5 @@
+#![allow(clippy::let_underscore_drop)]
+
+mod regression {
+    automod::dir!("tests/regression");
+}