selftests/seccomp: Set NNP for TSYNC ESRCH flag test

The TSYNC ESRCH flag test will fail for regular users because NNP was
not set yet. Add NNP setting.

Fixes: 51891498f2da ("seccomp: allow TSYNC and USER_NOTIF together")
Cc: [e-mail]
Reviewed-by: Tycho Andersen <[e-mail]>
Signed-off-by: Kees Cook <[e-mail]>

tools/testing/selftests/seccomp/seccomp_bpf.c

···
 	int ret;
 	unsigned int flags;
 
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+
 	/* these were exclusive */
 	flags = SECCOMP_FILTER_FLAG_NEW_LISTENER |
 		SECCOMP_FILTER_FLAG_TSYNC;