openssh unix dev - Apr 2018 - OpenSSH_6.0p1 - configure: WARNING: zlib.h: present but cannot be compiled

Hello,
          I am having difficulty upgrading OpenSSH_6.0p1 to any higher version
from OpenSSH_6.1p1 to OpenSSH_7.6p1. I keep getting the same error below:
Any thoughts or concerns? Am I missing something here.

Thanks in advance,

checking zlib.h usability... no
checking zlib.h presence... yes
configure: WARNING: zlib.h: present but cannot be compiled
configure: WARNING: zlib.h:     check for missing prerequisite headers?
configure: WARNING: zlib.h: see the Autoconf documentation
configure: WARNING: zlib.h:     section "Present But Cannot Be
Compiled"
configure: WARNING: zlib.h: proceeding with the compiler's result
configure: WARNING:     ## ------------------------------------------- ##
configure: WARNING:     ## Report this to openssh-unix-dev at
mindrot.org<mailto:openssh-unix-dev at mindrot.org> ##
configure: WARNING:     ## ------------------------------------------- ##
checking for zlib.h... no
configure: error: *** zlib.h missing - please install first or check config.log
***


ssh -V
OpenSSH_6.0p1, OpenSSL 1.0.2j  26 Sep 2016

find / -name zlib.h
/opt/freeware/include/zlib.h
/usr/include/zlib.h
/usr/local/include/zlib.h

On 19 April 2018 at 09:20, Tom Nielsen <Tom.Nielsen at smilebrands.com>
wrote:
>           I am having difficulty upgrading OpenSSH_6.0p1 to any higher
version from OpenSSH_6.1p1 to OpenSSH_7.6p1. I keep getting the same error
below:
> Any thoughts or concerns? Am I missing something here.
What kind of system and compiler is this?  The compilation of the zlib
test seems to have failed and you should be able the reason in
config.log (it'll be a fair way up from the bottom of the file).


-- 
Darren Tucker (dtucker at dtucker.net)
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