Meson includes the same logic that tries to look for -lz if
pkg-config (and cmake) cannot find zlib. The undocumented
--disable-zlib-test option becomes a no-op.
There is still an instance of "-lz" in the LIBS directory.
It will go away as soon as tests are converted to meson,
because the zlib dependency does not propagate from libblock.fa
to the Makefile-build unit tests.