Update location for zlib 1.2.12 as original location is no longer available.
zlib.net removed the 1.2.12 version of zlib when they released the 1.2.13 version on October 13th.
Github still keeps it around, so use that instead.
zlib.net removed the 1.2.12 version of zlib when they released the 1.2.13 version on October 13th.
Github still keeps it around, so use that instead.