New mail notifier: Allow build without QtTextToSpeech

Made optional by commit f7bac15b pending a port to Qt6.

agents/newmailnotifier/CMakeLists.txt

@@ -42,7 +42,6 @@ target_link_libraries( akonadi_newmailnotifier_agent
   KF5::Notifications
   KF5::Service
   KF5::I18n
-  Qt::TextToSpeech
 )
 
 if(Qt5TextToSpeech_FOUND)

agents/newmailnotifier/newmailnotifiersettingswidget.cpp

@@ -179,8 +179,8 @@ void NewMailNotifierSettingsWidget::load()
     mExcludeMySelf->setChecked(settings->excludeEmailsFromMe());
     mAllowToShowMail->setChecked(settings->showButtonToDisplayMail());
     mKeepPersistentNotification->setChecked(settings->keepPersistentNotification());
-    mTextToSpeak->setChecked(settings->textToSpeakEnabled());
 #if HAVE_TEXT_TO_SPEECH_SUPPORT
+    mTextToSpeak->setChecked(settings->textToSpeakEnabled());
     mTextToSpeakSetting->setEnabled(mTextToSpeak->isChecked());
     mTextToSpeakSetting->setText(settings->textToSpeak());
 #endif