Created attachment 477912 [details] patch output openssh-7.5_p1-r2 uses X509 patch version 10.2, and I guess it contains libressl-related fix already. It just compiled without error by dropping openssh-7.5p1-x509-libressl.patch.
Fixed https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=dab716d567737f341d4bdbc64f81f4a3f6bfe260