Fixed build failure when building without thread support

src/b6b_exc.c

@@ -23,7 +23,9 @@ static enum b6b_res b6b_exc_proc_try(struct b6b_interp *interp,
 {
 	struct b6b_obj *t, *e, *f, *o;
 	unsigned int argc;
+#ifdef B6B_HAVE_THREADS
 	int exit;
+#endif
 	enum b6b_res res, eres = B6B_ERR, fres;
 
 	argc = b6b_proc_get_args(interp, args, "oo|oo", NULL, &t, &e, &f);
@@ -55,12 +57,16 @@ static enum b6b_res b6b_exc_proc_try(struct b6b_interp *interp,
 		exit = interp->exit;
 		/* if the try block triggered exit, postpone it and let the finally
 		 * block run */
+#ifdef B6B_HAVE_THREADS
 		interp->exit = 0;
+#endif
 		o = b6b_ref(interp->fg->_);
 		fres = b6b_call(interp, f);
 		b6b_unref(interp->fg->_);
 		interp->fg->_ = o;
+#ifdef B6B_HAVE_THREADS
 		interp->exit = exit;
+#endif
 
 		if ((res == B6B_RET) || (res == B6B_EXIT))
 			return res;