check flags passed to rb_nogvl()

RB_NOGVL_UBF_ASYNC_SAFE is wrongly specified because flags
is not checked.
[Bug #15499] 23444302

(cherry picked from commit ff98931daca1265e5bd33025d160c77e452c399e)

1 files changed, 1 insertions, 1 deletions

diff --git a/thread.c b/thread.c
index 17bc1e75ae..708aaa471d 100644
--- a/thread.c
+++ b/thread.c
@@ -1464,7 +1464,7 @@ rb_nogvl(void *(*func)(void *), void *data1,
 	data2 = th;
     }
     else if (ubf && vm_living_thread_num(th->vm) == 1) {
-        if (RB_NOGVL_UBF_ASYNC_SAFE) {
+        if (flags & RB_NOGVL_UBF_ASYNC_SAFE) {
             th->vm->ubf_async_safe = 1;
         }
         else {