security/libssh: Update to 0.12.0
Changes: https://git.libssh.org/projects/libssh.git/tree/CHANGELOG
Security: CVE-2026-0964, CVE-2026-0965, CVE-2026-0966, CVE-2026-0967, CVE-2026-0968, CVE-2025-14821
(cherry picked from commit c05ae97377204ae6dcf1a2ee00cf647804342bed)