Use build logic provided by toolchain instead of doing it manually.

Signed-off-by: Daniel Engberg <daniel.engberg.lists@pyret.net>

This adds two optimizations for ARM:
NEON optimized Adler(-)32 checksum algorithm (ARMv7 and newer NEON CPUs)
ARM(v7+) specific optimization for inflate
I've also connected inflate optimization to the build using the following
source as template.
mirror/chromium@0397489#diff-a62ad2db6c83dbc205d34bb9a8884f16

Additional info:
https://codereview.chromium.org/2676493007/
https://codereview.chromium.org/2722063002/

Sources:
madler/zlib#251 (only the first commit)
madler/zlib#256

Signed-off-by: Daniel Engberg <daniel.engberg.lists@pyret.net>

Add option to use O3 optimization as not all devices have
space constraints. This option is default using GCC in upstream
but isn't in the CMake makefile for some reason.

Source: https://github.com/madler/zlib/blob/master/configure#L170

Signed-off-by: Daniel Engberg <daniel.engberg.lists@pyret.net>

Some packages such as Python/Python3 (host pip/pip3) needs this
to compile.

More detailed explanation provided by Alexandru:

"i need the zlib/host for Python/Python3 ; because, it seems the
host pip/pip3 needs this to work ; i suspect in older versions
this worked, because some of the host's build env would be used
in the build, and then the zlib-dev from the host distro would
be used ; now, the host-build does not seem to have any
-I/usr/include stuff, which is good

and it also seems that Python/Python3 does not like it if the
zlib-dev package is too old, so using this zlib/host would be
good for this as well"

Source:
#1329 (comment)

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Signed-off-by: Daniel Engberg <daniel.engberg.lists@pyret.net>