[infra] Add libzstd from cipd to mesa builds

The pre-built version of llvm-deps that we pull from cipd was built with
libzstd support, so has references to it, but the CF bots do not have a
system installed version of the library to compile against.

Thankfully libzstd is already in cipd, so we can just pullg the most
recent stable version of that and point meson at it for the mesa builds.

This CL also re-enables the usage of libzstd in mesa itself, since we
cannot avoid this dependency, unless we are going to handroll llvm (llvm
is a hard dependency for the software drivers that are needed for the
fuzzers, so cannot be dropped).

Bug: 475840957
Change-Id: Id20d68a346a5dc0bcf0e790cafb609780094df45
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/328775
Auto-Submit: Ryan Harrison <rharrison@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: James Price <jrprice@google.com>