How to use GtkPopoverMenuBar in GTK4?

Question

Currently, I'm trying to use GtkPopoverMenuBar widget in a GTK4 app in C, based on the tutorial listed here: https://toshiocp.github.io/Gtk4-tutorial/sec17.html

Here's the current code I have:

#include <gtk/gtk.h>

static void
quit_activated(GSimpleAction *action, GVariant *parameter, GApplication *application) {
    g_application_quit (application);
}

static void
app_activate (GApplication *application) {
  GtkApplication *app = GTK_APPLICATION (application);
  GtkWidget *win = gtk_application_window_new (GTK_APPLICATION (app));
  gtk_window_set_title (GTK_WINDOW (win), "menu1");
  gtk_window_set_default_size (GTK_WINDOW (win), 400, 300);

  gtk_application_window_set_show_menubar (GTK_APPLICATION_WINDOW (win), TRUE);
  gtk_window_present (GTK_WINDOW (win));
}

static void
app_startup (GApplication *application) {
  GtkApplication *app = GTK_APPLICATION (application);
  //GtkWidget *win = GTK_WIDGET(gtk_application_get_active_window(app));
  //GtkWidget *boxv = gtk_window_get_child(GTK_WINDOW(win));

  GSimpleAction *act_quit = g_simple_action_new ("quit", NULL);
  g_action_map_add_action (G_ACTION_MAP (app), G_ACTION (act_quit));
  g_signal_connect (act_quit, "activate", G_CALLBACK (quit_activated), application);

  GMenu *menubar = g_menu_new ();
  GtkPopoverMenuBar *popover_menubar = gtk_popover_menu_bar_new_from_model (menubar);
  GMenuItem *menu_item_file = g_menu_item_new ("File", NULL);
  GMenu *menu = g_menu_new ();
  GMenuItem *menu_item_quit = g_menu_item_new ("Quit", "app.quit");
  g_menu_append_item (menu, menu_item_quit);
  g_object_unref (menu_item_quit);
  g_menu_item_set_submenu (menu_item_file, G_MENU_MODEL (menu));
  g_menu_append_item (menubar, menu_item_file);
  g_object_unref (menu_item_file);

  //gtk_box_pack_start(GTK_BOX(boxv), GTK_WIDGET(popover_menubar), TRUE, FALSE, 0);

  gtk_application_set_menubar (GTK_APPLICATION (app), G_MENU_MODEL (menubar));
}

#define APPLICATION_ID "com.github.ToshioCP.menu1"

int
main (int argc, char **argv) {
  GtkApplication *app;
  int stat;

  app = gtk_application_new (APPLICATION_ID, G_APPLICATION_DEFAULT_FLAGS);
  g_signal_connect (app, "startup", G_CALLBACK (app_startup), NULL);
  g_signal_connect (app, "activate", G_CALLBACK (app_activate), NULL);

  stat = g_application_run (G_APPLICATION (app), argc, argv);
  g_object_unref (app);
  return stat;
}

But there's a problem: The GCC compiler won't recognise the gtk/gtkpopovermenubar.h library.

It says: identifier "GtkPopoverMenuBar" is undefined

I'm using VSCode, with this configuration in tasks.json:

{
    "tasks": [
        {
            "type": "cppbuild",
            "label": "C/C++: gcc.exe build active file",
            "command": "C:\\msys64\\mingw64\\bin\\gcc.exe",
            "args": [
                "-fdiagnostics-color=always",
                "-g",
                "-IC:/msys64/mingw64/bin/../include/libadwaita-1",
                "-IC:/msys64/mingw64/bin/../include/gtk-4.0",
                "-IC:/msys64/mingw64/bin/../include/pango-1.0",
                "-IC:/msys64/mingw64/bin/../include",
                "-IC:/msys64/mingw64/bin/../include/glib-2.0",
                "-IC:/msys64/mingw64/bin/../lib/glib-2.0/include",
                "-IC:/msys64/mingw64/bin/../include/harfbuzz",
                "-IC:/msys64/mingw64/bin/../include/freetype2",
                "-IC:/msys64/mingw64/bin/../include/libpng16",
                "-IC:/msys64/mingw64/bin/../include/fribidi",
                "-IC:/msys64/mingw64/bin/../include/cairo",
                "-IC:/msys64/mingw64/bin/../include/pixman-1",
                "-IC:/msys64/mingw64/bin/../include/gdk-pixbuf-2.0",
                "-IC:/msys64/mingw64/bin/../include/webp",
                "-IC:/msys64/mingw64/bin/../include/graphene-1.0",
                "-IC:/msys64/mingw64/bin/../lib/graphene-1.0/include",
                "${file}",
                "-LC:/msys64/mingw64/bin/../lib",
                "-ladwaita-1",
                "-lgtk-4",
                "-lpangowin32-1.0",
                "-lpangocairo-1.0",
                "-lpango-1.0",
                "-lharfbuzz",
                "-lgdk_pixbuf-2.0",
                "-lcairo-gobject",
                "-lcairo",
                "-lgraphene-1.0",
                "-lgio-2.0",
                "-lgobject-2.0",
                "-lglib-2.0",
                "-lintl",
                "-o",
                "${fileDirname}\\..\\bin\\${fileBasenameNoExtension}.exe"
            ],
            "options": {
                "cwd": "${fileDirname}"
            },
            "problemMatcher": [
                "$gcc"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "detail": "Task generated by Debugger."
        }
    ],
    "version": "2.0.0"
}

gtk.h is in the includes and in the linker. And it links to gtkpopovermenubar.h, yet it doesn't show up when typing, nor does it compile.

What do I need to do to get GtkPopoverMenuBar function working? Any help would be greatly appreciated!