sshkey.c references sshsk_sign(), which is defined in ${SKSRCS}.
Due to how FreeBSD builds libssh, or put differently, due to upstream
not building a shared libssh.so, we need to partially revert
65d8491719bb ("secure: Adapt Makefile to ssh-sk-client everywhere"), and
add ${SKSRCS} back, to avoid linking problems, especially when building
with GCC:
/usr/local/bin/ld: /usr/obj/usr/src/amd64.amd64/secure/lib/libssh/libprivatessh.so: undefined reference to `sshsk_sign' collect2: error: ld returned 1 exit status`
Put the sources in a separate line, to maintain line-by-line
compatibility with upstream Makefile.in
PR: 286580
Fixes: 65d8491719bb ("secure: Adapt Makefile to ssh-sk-client everywhere")