wasm: don't create a wasm global for dyld poison

There's a much more efficient way to convert an unsigned i32 to a
signed one. Thanks, o3-mini-high.

(cherry picked from commit 75fcc5c9)

utils/jsffi/dyld.mjs

@@ -231,10 +231,7 @@ class DyLD {
   // memory access near this address will trap immediately.
   //
   // In JS API i32 is signed, hence this layer of redirection.
-  static #poison = new WebAssembly.Global(
-    { value: "i32", mutable: false },
-    0xffffffff - DyLD.#pageSize
-  ).value;
+  static #poison = (0xffffffff - DyLD.#pageSize) | 0;
 
   // When processing exports, skip the following ones since they're
   // generated by wasm-ld.