fix build when lua-devel libs are not available

Without this, the following error occurs:

ld: trigger.o: in function `do_trigger':
sc-im/src/trigger.c:222: undefined reference to `doLuaTrigger_cell'
collect2: error: ld returned 1 exit status

1 files changed, 2 insertions, 0 deletions

diff --git a/src/trigger.c b/src/trigger.c
index 803356f..815a3e5 100644
--- a/src/trigger.c
+++ b/src/trigger.c
@@ -217,10 +217,12 @@ void do_trigger(struct ent *p , int rw) {
     if(in_trigger) return;
     in_trigger = 1;
 
+#ifdef XLUA
     if ((trigger->flag & TRG_LUA ) == TRG_LUA) {
         sc_info("%d %d", p->row, p->col);
         doLuaTrigger_cell(p,rw);
     }
+#endif
 
     if ((trigger->flag & TRG_C ) == TRG_C) {
         do_C_Trigger_cell(p,rw);