tools/nolibc: fix build of the test case using glibc

Some extra tests for various integer types and limits were added by
commit d1209597ff ("tools/nolibc: add tests for the integer limits
in stdint.h"), but we forgot to retest with glibc. Stddef and stdint
are now needed for the program to build there.

Cc: Vincent Dagonneau <v@vda.io>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/nolibc/nolibc-test.c

@@ -34,6 +34,8 @@
 #include <sched.h>
 #include <signal.h>
 #include <stdarg.h>
+#include <stddef.h>
+#include <stdint.h>
 #include <unistd.h>
 #endif
 #endif