Merge branch 'rs/zip-tests'

Update zip tests to skip some that cannot be handled on platform
unzip.

* rs/zip-tests:
  t5003: check if unzip supports symlinks
  t5000, t5003: move ZIP tests into their own script
  t0024, t5000: use test_lazy_prereq for UNZIP
  t0024, t5000: clear variable UNZIP, use GIT_UNZIP instead

diff --cc t/test-lib.sh
Simple merge