cmake: Make mac vcam optional (enabled by default)

plugins/CMakeLists.txt

@@ -30,7 +30,10 @@ elseif(APPLE)
 	add_subdirectory(mac-capture)
 	add_subdirectory(mac-vth264)
 	add_subdirectory(mac-syphon)
-	add_subdirectory(mac-virtualcam)
+	option(BUILD_VIRTUALCAM "Build Virtualcam" ON)
+	if(BUILD_VIRTUALCAM)
+		add_subdirectory(mac-virtualcam)
+	endif()
 	add_subdirectory(decklink/mac)
 	add_subdirectory(vlc-video)
 	add_subdirectory(linux-jack)