[ssh_x509] logging in signal handler with GNU C library

[ssh_x509 at roumenpetrov.info]

Hello,


Related to OpenSSH CVE-2024-6387.

With commit "in alarm handler do not send alarm to "preauth" child" 
PKIX-SSH 13.3.2 enables logging in signal handler on all OS-es. Before 
it was only on OpenBSD. Unfortunately this still cannot be considered 
secure on system with GNU C library. It is demonstrated code execution 
on 32-bit Linux/glibc.

In master branch commit "disable again log in sigdie()" restores 
previous state.
Manual correction is open log.c, find function sshsigdie and change 
preprocessor directive from "#if 1" to "#if 0".


Regards
Roumen