[meta] Use named predicates for x86 settings in the Rust crate too;

And generate them using the same deterministic order that the Python
code uses.

cranelift/codegen/meta/src/cdsl/mod.rs

@@ -23,6 +23,15 @@ macro_rules! predicate {
     ($a:ident && $($b:tt)*) => {
         PredicateNode::And(Box::new($a.into()), Box::new(predicate!($($b)*)))
     };
+    (!$a:ident && $($b:tt)*) => {
+        PredicateNode::And(
+            Box::new(PredicateNode::Not(Box::new($a.into()))),
+            Box::new(predicate!($($b)*))
+        )
+    };
+    (!$a:ident) => {
+        PredicateNode::Not(Box::new($a.into()))
+    };
     ($a:ident) => {
         $a.into()
     };