Add _SC_NSIG.

https://pubs.opengroup.org/onlinepubs/9799919799.2024edition/functions/sysconf.html (2024) says "Austin Group Defect 741 is applied, adding _SC_NSIG".

Change-Id: Ic8372105bac153403ab41369805c46322c25013e
diff --git a/tests/headers/posix/unistd_h.c b/tests/headers/posix/unistd_h.c
index f66609d..fdd7bde 100644
--- a/tests/headers/posix/unistd_h.c
+++ b/tests/headers/posix/unistd_h.c
@@ -221,6 +221,9 @@
   MACRO(_SC_MQ_OPEN_MAX);
   MACRO(_SC_MQ_PRIO_MAX);
   MACRO(_SC_NGROUPS_MAX);
+#if defined(__BIONIC__) // New in POSIX 2024.
+  MACRO(_SC_NSIG);
+#endif
   MACRO(_SC_OPEN_MAX);
   MACRO(_SC_PAGE_SIZE);
   MACRO(_SC_PAGESIZE);