build: ensure we set ENABLE_LUA_OLD when using a lua interpreter

We missed to actually set the ENABLE_LUA_OLD. Ross run into some
problems with Lua 5.2 builds and we hope this fixes the issue for him.

Found and fixed by Marcel Hollerbach (only put in the system by me).

Fixes T8705

diff --git a/meson.build b/meson.build
index 5732d85..e73425c 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -267,6 +267,7 @@ luaold_interpreters = [
 lua_pc_name = ''
 
 if get_option('lua-interpreter') == 'lua'
+  config_h.set('ENABLE_LUA_OLD', '1')
   foreach l : luaold_interpreters
     lua = dependency(l[0], version: l[1], required:false)
     lua_pc_name = l[0]