feat(audio): make the libfilteraudio dependency optional

cmake/Dependencies.cmake

@@ -117,7 +117,6 @@ if (NOT TOXCORE_FOUND OR
 endif()
 
 search_dependency(OPENAL              PACKAGE openal)
-search_dependency(FILTERAUDIO         LIBRARY filteraudio)
 
 if (PLATFORM_EXTENSIONS AND UNIX AND NOT APPLE)
   # Automatic auto-away support. (X11 also using for capslock detection)

src/audio/audio.cpp

@@ -19,7 +19,9 @@
 
 #include "audio.h"
 #include "src/audio/backend/openal.h"
+#ifdef USE_FILTERAUDIO
 #include "src/audio/backend/openal2.h"
+#endif
 #include "src/persistence/settings.h"
 
 #include <QDebug>
@@ -167,6 +169,7 @@
  */
 Audio& Audio::getInstance()
 {
+#ifdef USE_FILTERAUDIO
     static bool initialized = false;
     static bool Backend2 = false;
 
@@ -178,7 +181,9 @@ Audio& Audio::getInstance()
     if (Backend2) {
         static OpenAL2 instance;
         return instance;
-    } else {
+    } else
+#endif
+    {
         static OpenAL instance;
         return instance;
     }

src/widget/form/settings/avform.cpp

@@ -60,6 +60,9 @@ AVForm::AVForm()
 
     cbEnableTestSound->setToolTip(tr("Play a test sound while changing the output volume."));
 
+#ifndef USE_FILTERAUDIO
+    cbEnableBackend2->setVisible(false);
+#endif
     cbEnableBackend2->setChecked(s.getEnableBackend2());
 
     connect(rescanButton, &QPushButton::clicked, this, &AVForm::rescanDevices);