fix(qt): make Qt6 optional

app/CMakeLists.txt

@@ -13,13 +13,13 @@ OPTION(USE_FERVOR "Add Fervor support" OFF)
 OPTION(CALYP_MANAGED_RESOURCES "Handle streams in separate threads" ON)
 OPTION(CALYP_THREADED_MODULES "Use threads for modules" ON)
 
-if(${USE_QT6})
-FIND_PACKAGE(Qt6 REQUIRED COMPONENTS Core Gui Widgets Concurrent)
-IF (NOT Qt6_FOUND)
-FIND_PACKAGE(Qt5 REQUIRED COMPONENTS Core Gui Widgets Concurrent)
-ENDIF()
+IF(${USE_QT6})
+  FIND_PACKAGE(Qt6 QUIET COMPONENTS Core Gui Widgets Concurrent)
+  IF (NOT Qt6_FOUND)
+    FIND_PACKAGE(Qt5 REQUIRED COMPONENTS Core Gui Widgets Concurrent)
+  ENDIF()
 ELSE()
-FIND_PACKAGE(Qt5 REQUIRED COMPONENTS Core Gui Widgets Concurrent)
+  FIND_PACKAGE(Qt5 REQUIRED COMPONENTS Core Gui Widgets Concurrent)
 ENDIF()
 
 ADD_SUBDIRECTORY(external)