wasm: fix FinalizationRegistry logic for Cloudflare Workers

This patch fixes FinalizationRegistry related logic for Cloudflare
Workers in wasm backend js post linker. Cloudflare Workers doesn't
support FinalizationRegistry, in this case we use a dummy
implementation that doesn't do anything.

(cherry picked from commit bea8ea4c)

utils/jsffi/post-link.mjs

@@ -62,7 +62,7 @@ export async function postLink(mod) {
   // Keep this in sync with dyld.mjs!
   src = `${src}\nexport default (__exports) => {`;
   src = `${src}\nconst __ghc_wasm_jsffi_jsval_manager = new JSValManager();`;
-  src = `${src}\nconst __ghc_wasm_jsffi_finalization_registry = new FinalizationRegistry(sp => __exports.rts_freeStablePtr(sp));`;
+  src = `${src}\nconst __ghc_wasm_jsffi_finalization_registry = globalThis.FinalizationRegistry ? new FinalizationRegistry(sp => __exports.rts_freeStablePtr(sp)) : { register: () => {}, unregister: () => true };`;
   src = `${src}\nreturn {`;
   src = `${src}\nnewJSVal: (v) => __ghc_wasm_jsffi_jsval_manager.newJSVal(v),`;
   src = `${src}\ngetJSVal: (k) => __ghc_wasm_jsffi_jsval_manager.getJSVal(k),`;