### Godot version

any version after 74458b6

### System information

Linux x64, but likely irrelevant

### Issue description

OpenXR action maps are not properly exported in recent builds of Godot 4: the `.res` file is small and does no longer seem to contain anything of use. In-game, no actions are passed on to OpenXR (obviously).

I bisected the issue down to https://github.com/godotengine/godot/commit/74458b6e9bed0f28db3374c7406eacbcf4b09b9d, which was merged in #70377.

### Steps to reproduce

1. Delete any previous export files (`.godot/exported/*/*.pkg`)
2. Perform an export (I did one for Android, but it likely works with anything)
3. Observe OpenXR actions not working in the export (error spam 'sync_action_sets: Condition "active_sets.size() == 0"'), and the exported action map file being very small (`.godot/exported/*/*.pkg`, from a few tens of kilobytes down to 296 bytes)

### Minimal reproduction project

Any OpenXR project can be used, such as https://github.com/BastiaanOlij/godot4_openxr_demo
if (!f.is_empty()) {
				custom_list.push_back(f);
			}
		}
	}
	for (int i = 0; i < export_plugins.size(); i++) {
		custom_list.append_array(export_plugins[i]->_get_export_features(Ref<EditorExportPlatform>(this), p_debug));
	}
	ProjectSettings::CustomMap custom_map;
	if (path_remaps.size()) {
		if (true) { 
			for (int i = 0; i < path_remaps.size(); i += 2) {
				String from = path_remaps[i];
				String to = path_remaps[i + 1];
				String remap_file = "[remap]\n\npath=\"" + to.c_escape() + "\"\n";
				CharString utf8 = remap_file.utf8();
				Vector<uint8_t> new_file;
				new_file.resize(utf8.length());
				for (int j = 0; j < utf8.length(); j++) {
					new_file.write[j] = utf8[j];
				}
				err = p_func(p_udata, from + ".remap", new_file, idx, total, enc_in_filters, enc_ex_filters, key);
				if (err != OK) {
					return err;
				}
			}
		} else {
			
			custom_map["path_remap/remapped_paths"] = path_remaps;
		}