UI: Find Qt WinExtras only in Qt 5

WinExtras does not exist in Qt 6. Only try to find it and link against
it if using Qt 5.

UI/CMakeLists.txt

@@ -72,10 +72,15 @@ find_package(CURL REQUIRED)
 add_subdirectory(frontend-plugins)
 add_executable(obs)
 
+set(UI_COMPONENTS_WIN "")
+if(QT_VERSION EQUAL 5)
+  set(UI_COMPONENTS_WIN "WinExtras")
+endif()
+
 find_qt(
   VERSION ${QT_VERSION}
   COMPONENTS Widgets Network Svg Xml
-  COMPONENTS_WIN WinExtras
+  COMPONENTS_WIN ${UI_COMPONENTS_WIN}
   COMPONENTS_LINUX Gui)
 
 target_link_libraries(obs PRIVATE Qt::Widgets Qt::Svg Qt::Xml Qt::Network)
@@ -338,7 +343,11 @@ if(OS_WINDOWS)
             win-update/win-update-helpers.hpp
             ${CMAKE_BINARY_DIR}/obs.rc)
 
-  target_link_libraries(obs PRIVATE crypt32 OBS::blake2 Qt::WinExtras)
+  if(QT_VERSION EQUAL 5)
+    target_link_libraries(obs PRIVATE crypt32 OBS::blake2 Qt::WinExtras)
+  else()
+    target_link_libraries(obs PRIVATE crypt32 OBS::blake2)
+  endif()
 
   target_compile_features(obs PRIVATE cxx_std_17)