fix: resolve Qt MOC generation for conditionally compiled UpdaterDialog

Move UpdaterDialog class declaration outside #ifdef _WIN32 to ensure
Qt's MOC can see the Q_OBJECT macro. Add stub implementations for
non-Windows platforms to satisfy linker.

Signed-off-by: Zephyron <zephyron@citron-emu.org>

src/citron/updater/updater_dialog.cpp

@@ -1,8 +1,9 @@
-#ifdef _WIN32
 // SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include "citron/updater/updater_dialog.h"
+
+#ifdef _WIN32
 #include "ui_updater_dialog.h"
 
 #include <QApplication>
@@ -353,4 +354,45 @@ QString UpdaterDialog::GetUpdateMessage(Updater::UpdaterService::UpdateResult re
 
 #include "updater_dialog.moc"
 
+#else // _WIN32
+
+// Forward declarations for non-Windows platforms
+namespace Updater {
+struct UpdateInfo {};
+class UpdaterService {
+public:
+    enum class UpdateResult { Success };
+};
+}
+
+// Stub implementations for non-Windows platforms
+UpdaterDialog::UpdaterDialog(QWidget* parent) : QDialog(parent) {}
+UpdaterDialog::~UpdaterDialog() = default;
+void UpdaterDialog::CheckForUpdates(const std::string&) {}
+void UpdaterDialog::ShowUpdateAvailable(const Updater::UpdateInfo&) {}
+void UpdaterDialog::ShowUpdateChecking() {}
+void UpdaterDialog::OnUpdateCheckCompleted(bool, const Updater::UpdateInfo&) {}
+void UpdaterDialog::OnUpdateDownloadProgress(int, qint64, qint64) {}
+void UpdaterDialog::OnUpdateInstallProgress(int, const QString&) {}
+void UpdaterDialog::OnUpdateCompleted(Updater::UpdaterService::UpdateResult, const QString&) {}
+void UpdaterDialog::OnUpdateError(const QString&) {}
+void UpdaterDialog::OnDownloadButtonClicked() {}
+void UpdaterDialog::OnCancelButtonClicked() {}
+void UpdaterDialog::OnCloseButtonClicked() {}
+void UpdaterDialog::OnRestartButtonClicked() {}
+void UpdaterDialog::SetupUI() {}
+void UpdaterDialog::ShowCheckingState() {}
+void UpdaterDialog::ShowNoUpdateState() {}
+void UpdaterDialog::ShowUpdateAvailableState() {}
+void UpdaterDialog::ShowDownloadingState() {}
+void UpdaterDialog::ShowInstallingState() {}
+void UpdaterDialog::ShowCompletedState() {}
+void UpdaterDialog::ShowErrorState() {}
+void UpdaterDialog::UpdateDownloadProgress(int, qint64, qint64) {}
+void UpdaterDialog::UpdateInstallProgress(int, const QString&) {}
+QString UpdaterDialog::FormatBytes(qint64) const { return QString(); }
+QString UpdaterDialog::GetUpdateMessage(Updater::UpdaterService::UpdateResult) const { return QString(); }
+
+#include "updater_dialog.moc"
+
 #endif // _WIN32

src/citron/updater/updater_dialog.h

@@ -3,10 +3,10 @@
 
 #pragma once
 
-#ifdef _WIN32
-
 #include <memory>
 #include <QDialog>
+
+#ifdef _WIN32
 #include <QProgressBar>
 #include <QLabel>
 #include <QPushButton>
@@ -14,6 +14,13 @@
 #include <QTimer>
 
 #include "citron/updater/updater_service.h"
+#else
+// Forward declarations for non-Windows platforms
+namespace Updater {
+struct UpdateInfo;
+class UpdaterService;
+}
+#endif
 
 namespace Ui {
 class UpdaterDialog;
@@ -64,6 +71,7 @@ private:
     QString GetUpdateMessage(Updater::UpdaterService::UpdateResult result) const;
 
 private:
+#ifdef _WIN32
     std::unique_ptr<Ui::UpdaterDialog> ui;
     std::unique_ptr<Updater::UpdaterService> updater_service;
 
@@ -85,6 +93,5 @@ private:
     qint64 total_download_size = 0;
     qint64 downloaded_bytes = 0;
     QTimer* progress_timer;
-};
-
-#endif // _WIN32
+#endif // _WIN32
+};