Change how flags are stored in serialized modules.

This commit changes how both the shared flags and ISA flags are stored in the
serialized module to detect incompatibilities when a serialized module is
instantiated.

It improves the error reporting when a compiled module has mismatched shared
flags.

cranelift/codegen/src/isa/x86/mod.rs

@@ -21,12 +21,7 @@ use crate::isa::{EncInfo, RegClass, RegInfo, TargetIsa};
 use crate::regalloc;
 use crate::result::CodegenResult;
 use crate::timing;
-use alloc::{
-    borrow::{Cow, ToOwned},
-    boxed::Box,
-    string::String,
-    vec::Vec,
-};
+use alloc::{borrow::Cow, boxed::Box, vec::Vec};
 use core::any::Any;
 use core::fmt;
 use core::hash::{Hash, Hasher};
@@ -83,15 +78,8 @@ impl TargetIsa for Isa {
         &self.shared_flags
     }
 
-    fn enabled_isa_flags(&self) -> Vec<String> {
-        self.isa_flags
-            .iter_enabled()
-            .map(ToOwned::to_owned)
-            .collect()
-    }
-
-    fn is_flag_enabled(&self, flag: &str) -> bool {
-        self.isa_flags.is_enabled(flag)
+    fn isa_flags(&self) -> Vec<shared_settings::Value> {
+        self.isa_flags.iter().collect()
     }
 
     fn hash_all_flags(&self, mut hasher: &mut dyn Hasher) {

cranelift/codegen/src/isa/x86/settings.rs

@@ -1,6 +1,6 @@
 //! x86 Settings.
 
-use crate::settings::{self, detail, Builder};
+use crate::settings::{self, detail, Builder, Value};
 use core::fmt;
 
 // Include code generated by `cranelift-codegen/meta/src/gen_settings.rs:`. This file contains a