[embind] Add pointer policies for setting val object properties. (#24811)

After #24175, `val` required a pointer policy when creating a `val` with
a pointer. In `val.set(key, value)`, a temporary `val` object is
created, but there was no way to set the policy from user code. This
patch allows the user to pass in `allow_raw_pointers()` to enable this.

Author: brendandahl

system/include/emscripten/val.h

@@ -478,9 +478,9 @@ class EMBIND_VISIBILITY_DEFAULT val {
     return val(internal::_emval_get_property(as_handle(), val_ref(key).as_handle()));
   }
 
-  template<typename K, typename V>
-  void set(const K& key, const V& value) {
-    internal::_emval_set_property(as_handle(), val_ref(key).as_handle(), val_ref(value).as_handle());
+  template<typename K, typename V, typename... Policies>
+  void set(const K& key, const V& value, Policies... policies) {
+    internal::_emval_set_property(as_handle(), val_ref(key).as_handle(), val_ref(value, policies...).as_handle());
   }
 
   template<typename T>
@@ -609,9 +609,9 @@ class EMBIND_VISIBILITY_DEFAULT val {
     return BindingType<Ret>::fromWireType(result);
   }
 
-  template<typename T>
-  val val_ref(const T& v) const {
-    return val(v);
+  template<typename T, typename... Policies>
+  val val_ref(const T& v, Policies... policies) const {
+    return val(v, policies...);
   }
 
   const val& val_ref(const val& v) const {

test/embind/test_val.cpp

@@ -676,6 +676,13 @@ int main() {
   val::global().set("a", val::u16string(s));
   ensure_js("a == '😃 = \U0001F603 is :-D'");
 
+  test("val set() with policy");
+  Dummy *dummy = new Dummy();
+  val::global().set("a", dummy, allow_raw_pointers());
+  ensure_js("a instanceof Module.Dummy");
+  val::global().set("a", val::null());
+  delete dummy;
+
   printf("end\n");
   return 0;
 }

test/embind/test_val.out

@@ -1,3 +1,4 @@
+start
 test: val array()...
 test: template<typename T> val array(const std::vector<T> vec)...
 test: template<typename Iter> val array(Iter begin, Iter end)...
@@ -41,4 +42,5 @@ test: template<typename T> std::vector<T *> vecFromJSArray(const val& v)...
 test: template<typename T> std::vector<T> convertJSArrayToNumberVector(const val& v)...
 test: val u8string(const char* s)...
 test: val u16string(const char16_t* s)...
+test: val set() with policy...
 end