BUILD: fix FindMiniZip.cmake module to use pkg-config

On some distros the present logic will fail to detect
/usr/include/minizip/zip.h, use proper pkg-config call
to fix this. Regular cmake modules are broken and should
always be fixed to have some pkg-config logic, since it's the
only cross-distro standard to get correct library and include dirs.

If there is no pkg-config the module will fall back to the old find macros.