Use BTreeMap for NonstandardWitSection.adapters for determinism

In the `externref` code, we call `export_xform` while iterating
over `adapters` with `iter_mut`. Calling `export_xform` can result
in shims, with the id depending on the order in which we iterate
over the exports.

To make the final .wasm output deterministic, I've changed this to
use a `BTreeMap`, so that the iteration order doesn't depend on
the hashmap `RandomState`

crates/cli-support/src/js/mod.rs

@@ -2406,7 +2406,7 @@ impl<'a> Context<'a> {
 
     pub fn generate(&mut self) -> Result<(), Error> {
         self.prestore_global_import_identifiers()?;
-        for (id, adapter) in crate::sorted_iter(&self.wit.adapters) {
+        for (id, adapter) in self.wit.adapters.iter() {
             let instrs = match &adapter.kind {
                 AdapterKind::Import { .. } => continue,
                 AdapterKind::Local { instructions } => instructions,

crates/cli-support/src/wit/standard.rs

@@ -1,13 +1,14 @@
 use crate::descriptor::VectorKind;
 use crate::wit::{AuxImport, WasmBindgenAux};
 use std::borrow::Cow;
-use std::collections::{HashMap, HashSet};
+use std::collections::{BTreeMap, HashSet};
 use walrus::{FunctionId, ImportId, TypedCustomSectionId};
 
 #[derive(Default, Debug)]
 pub struct NonstandardWitSection {
     /// A list of adapter functions, keyed by their id.
-    pub adapters: HashMap<AdapterId, Adapter>,
+    // This is a `BTreeMap` so that we can use `iter_mut` with a deterministic order
+    pub adapters: BTreeMap<AdapterId, Adapter>,
 
     /// A list of pairs for adapter functions that implement core wasm imports.
     pub implements: Vec<(ImportId, FunctionId, AdapterId)>,