Use `objc_allocateClassPair` for `intrinsics.objc_register_class`

core/runtime/procs_darwin.odin

@@ -12,6 +12,7 @@ objc_SEL :: ^intrinsics.objc_selector
 foreign Foundation {
 	objc_lookUpClass :: proc "c" (name: cstring) -> objc_Class ---
 	sel_registerName :: proc "c" (name: cstring) -> objc_SEL ---
+	objc_allocateClassPair :: proc "c" (superclass: objc_Class, name: cstring, extraBytes: uint) ---
 
 	objc_msgSend        :: proc "c" (self: objc_id, op: objc_SEL, #c_vararg args: ..any) ---
 	objc_msgSend_fpret  :: proc "c" (self: objc_id, op: objc_SEL, #c_vararg args: ..any) -> f64 ---

src/check_builtin.cpp

@@ -225,6 +225,7 @@ void add_objc_proc_type(CheckerContext *c, Ast *call, Type *return_type, Slice<T
 
 	add_package_dependency(c, "runtime", "objc_lookUpClass");
 	add_package_dependency(c, "runtime", "sel_registerName");
+	add_package_dependency(c, "runtime", "objc_allocateClassPair");
 
 	add_package_dependency(c, "runtime", "objc_msgSend");
 	add_package_dependency(c, "runtime", "objc_msgSend_fpret");

src/llvm_backend_utility.cpp

@@ -1908,9 +1908,11 @@ lbValue lb_handle_objc_register_class(lbProcedure *p, Ast *expr) {
 	String name = tav.value.value_string;
 	lbAddr dst = lb_handle_objc_find_or_register_class(p, name);
 
-	auto args = array_make<lbValue>(permanent_allocator(), 1);
-	args[0] = lb_const_value(m, t_cstring, exact_value_string(name));
-	lbValue ptr = lb_emit_runtime_call(p, "objc_lookUpClass", args);
+	auto args = array_make<lbValue>(permanent_allocator(), 3);
+	args[0] = lb_const_nil(m, t_objc_Class);
+	args[1] = lb_const_nil(m, t_objc_Class);
+	args[2] = lb_const_int(m, t_uint, 0);
+	lbValue ptr = lb_emit_runtime_call(p, "objc_allocateClassPair", args);
 	lb_addr_store(p, dst, ptr);
 
 	return lb_addr_load(p, dst);