remove luajit header only dependency

Author: HeliumAnt

external/include/meson.build

@@ -6,8 +6,6 @@ external_inc_dirs = [include_directories('boost_1_75',
                                          'thread-pool-3.5.0/include',
                                          'hopscotch-map-2.3.1/include',)]
 if host_machine.system() in ['linux', 'darwin']
-  luajit_proj = subproject('LuaJIT-2.1', default_options: ['header_only=true'])
-  external_inc_dirs += luajit_proj.get_variable('luajit_source_dir')
 endif
 if host_machine.system() == 'windows'
   external_inc_dirs += include_directories('LZ4-1.9.3/LZ4',)