Silence unexpected-cfgs

library/stdarch/crates/assert-instr-macro/build.rs

@@ -2,6 +2,7 @@ use std::env;
 
 fn main() {
     println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo::rustc-check-cfg=cfg(optimized)");
     let opt_level = env::var("OPT_LEVEL")
         .ok()
         .and_then(|s| s.parse().ok())

library/stdarch/crates/core_arch/build.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("cargo::rustc-check-cfg=cfg(stdarch_intel_sde)");
+}