MiniZip 2.10.0 added support for zstd as a compression method, so we
should support it.
Note that a system version of zstd is preferred on Linux systems.
Enabled the MiniZip test tools for manual builds only. Info-ZIP hasn't
been updated in a while, so I'm going to use the MiniZip test tools to
compress ZIP archives using zstd.
Enabled MiniZip compression in order to compress stuff using the minizip
test program.
mz_strm_zstd.c: FIXME: Compression level doesn't work. Hard-coded the
maximum compression level for now.
