Fix CMake warning

CMake Warning (dev) at /usr/share/cmake-3.24/Modules/FindPackageHandleStandardArgs.cmake:438 (message):
  The package name passed to `find_package_handle_standard_args` (PkgConfig)
  does not match the name of the calling package (Lua).  This can lead to
  problems in calling code that expects `find_package` result variables
  (e.g., `_FOUND`) to follow a certain pattern.
Call Stack (most recent call first):
  /usr/share/cmake-3.24/Modules/FindPkgConfig.cmake:99 (find_package_handle_standard_args)
  cmake/FindLua.cmake:39 (include)
  CMakeLists.txt:571 (find_package)
This warning is for project developers.  Use -Wno-dev to suppress it.

cmake/FindLua.cmake

@@ -36,7 +36,10 @@
 # This is because, the lua location is not standardized and may exist in
 # locations other than lua/
 
-include(FindPkgConfig)
+if(NOT PKG_CONFIG_FOUND)
+  include(CMakeFindDependencyMacro)
+  find_dependency(PkgConfig)
+endif()
 
 unset(_lua_include_subdirs)
 unset(_lua_library_names)