[gdal] Fix linker error with static libpng#6305

Merged

vicroms merged 3 commits intomicrosoft:masterfrom

jumpinjackie:gdal-fix-static-libpng

May 6, 2019

Commits on May 4, 2019

When linking gdal with static libpng, it fails because the libpng vcpkg port has references to zlib symbols that aren't present in the internal copy of zlib that gdal builds/links against.
jumpinjackie
committed

Commits on May 6, 2019