Fix determinism of compiled modules (#3229)

* Fix determinism of compiled modules

Currently wasmtime's compilation artifacts are not deterministic due to
the usage of `HashMap` during serialization which has randomized order
of its elements. This commit fixes that by switching to a sorted
`BTreeMap` for various maps. A test is also added to ensure determinism.

If in the future the performance of `BTreeMap` is not as good as
`HashMap` for some of these cases we can implement a fancier
`serialize_with`-style solution where we sort keys during serialization,
but only during serialization and otherwise use a `HashMap`.

* fix lightbeam

crates/environ/src/compilation.rs

@@ -9,7 +9,7 @@ use anyhow::Result;
 use serde::{Deserialize, Serialize};
 use std::any::Any;
 use std::borrow::Cow;
-use std::collections::HashMap;
+use std::collections::BTreeMap;
 use std::fmt;
 use thiserror::Error;
 
@@ -204,10 +204,10 @@ pub trait Compiler: Send + Sync {
     fn triple(&self) -> &target_lexicon::Triple;
 
     /// Returns a list of configured settings for this compiler.
-    fn flags(&self) -> HashMap<String, FlagValue>;
+    fn flags(&self) -> BTreeMap<String, FlagValue>;
 
     /// Same as [`Compiler::flags`], but ISA-specific (a cranelift-ism)
-    fn isa_flags(&self) -> HashMap<String, FlagValue>;
+    fn isa_flags(&self) -> BTreeMap<String, FlagValue>;
 }
 
 /// Value of a configured setting for a [`Compiler`]