openssh-sshd: host contamination fix

openssh-sshd: host contamination fix

If you do a readelf -x .rodata /path/.../to/openssh/6.5p1-r0/packages-split/openssh-sshd/usr/sbin/sshd

You'll see two references to OE's sysroots/${BUILD_SYS} login and passwd binaries.
First one can be overridden with LOGIN_PROGRAM environment variable (see configure.ac),
second needs a cached variable definition.

(From OE-Core rev: 2127c80d0cc2a3a4d676bd3c0890454a175fba8e)

Signed-off-by: Matthieu Crapet <Matthieu.Crapet@ingenico.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>