fix lua and luajit conflict

CMakeLists.txt

@@ -82,6 +82,8 @@ find_package(GLEW REQUIRED)
 find_package(OpenAL REQUIRED)
 find_package(ZLIB REQUIRED)
 
+set(LIBS "")
+
 if (WIN32)
     if(VOXELENGINE_BUILD_WINDOWS_VCPKG)
       set(LUA_LIBRARIES "${CMAKE_CURRENT_SOURCE_DIR}/vcpkg/packages/luajit_x64-windows/lib/lua51.lib")
@@ -99,8 +101,9 @@ if (WIN32)
       add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/libs/glfw)
     endif()
 else()
-    # luajit has no CMakeLists.txt to use it as subdirectory, so install it manually
-    find_package(Lua REQUIRED)
+    find_package(PkgConfig)
+    pkg_check_modules(LUAJIT REQUIRED luajit)
+    set(LUA_LIBRARIES ${LUAJIT_LIBRARIES})
     find_package(PNG REQUIRED)
     set(PNGLIB PNG::PNG)
     set(VORBISLIB vorbis vorbisfile)
@@ -110,8 +113,6 @@ if (APPLE)
     find_package(glfw3 3.3 REQUIRED)
 endif ()
 
-set(LIBS "")
-
 if(UNIX)
     find_package(Threads REQUIRED)
     set(LIBS ${LIBS} Threads::Threads)