UI: Fix UI file changes not being picked up by CMake

Due to how CMake and generated project files are structured, just using
AUTOUIC to pick up Qt `.ui` files will lead to a situation where
changing such a file doesn't trigger a regeneration of the associated
header files and thus a re-build of the target.

Upstream fix still requires `.ui` files to be added as target sources.

CMake issue: https://gitlab.kitware.com/cmake/cmake/-/issues/17959

UI/frontend-plugins/frontend-tools/CMakeLists.txt

@@ -15,6 +15,10 @@ set_target_properties(
              AUTORCC ON
              AUTOUIC_SEARCH_PATHS "forms")
 
+target_sources(
+  frontend-tools PRIVATE forms/auto-scene-switcher.ui forms/captions.ui
+                         forms/output-timer.ui forms/scripts.ui)
+
 target_sources(
   frontend-tools
   PRIVATE frontend-tools.c
@@ -103,4 +107,15 @@ elseif(OS_POSIX)
   target_sources(frontend-tools PRIVATE auto-scene-switcher-nix.cpp)
 endif()
 
+get_target_property(_SOURCES frontend-tools SOURCES)
+set(_UI ${_SOURCES})
+list(FILTER _UI INCLUDE REGEX ".*\\.ui?")
+
+source_group(
+  TREE "${CMAKE_CURRENT_SOURCE_DIR}/forms"
+  PREFIX "UI Files"
+  FILES ${_UI})
+unset(_SOURCES)
+unset(_UI)
+
 setup_plugin_target(frontend-tools)