Update emscripten memory macro

lib/emscripten/src/macros.rs

@@ -1,6 +1,6 @@
 macro_rules! emscripten_memory_pointer {
-    ($memory:expr, $pointer:expr) => {
-        0 as usize
-        // unsafe { $memory.as_ptr().add($pointer as usize) }
-    };
+    ($memory:expr, $pointer:expr) => {{
+        use std::cell::Cell;
+        (&$memory.view::<u8>()[($pointer as usize)..]).as_ptr() as *mut Cell<u8> as *mut u8
+    }};
 }