Cardano Updates

kyua's signal-handling tests fail inside the Nix build sandbox on
aarch64-darwin: SIGTERM is delivered as SIGABRT and signal handlers
never fire (13/1443 tests fail).  Since atf depends on kyua as its
test runner, and libiconv depends on atf, the failure cascades through
the entire darwin stdenv — 633+ derivations including GHC and all
Haskell packages.

Disable atf's doCheck to break the cascade at the narrowest point.

Three fixes for eval 1182 failures:

1. proto-lens-etcd also uses proto-lens-setup's custom Setup.hs which
   invokes protoc at build time — add it alongside proto-lens-protobuf-types
   in hydraPkgs modules.  Fixes all hydra-native and hydra-static-musl builds.

2. cardano-node 10.7.0-pre links against snappy (new dependency).  Add a
   static-snappy overlay and pass -L to cardano-node ghcOptions on darwin so
   the linker picks the static archive instead of the nix store dylib.

3. fixup-nix-deps in packaging.nix was missing a libc++abi pattern, causing
   the zip checkPhase to reject binaries that reference the nix store copy.

Both hydraPkgs (via grapesy/grpc) and cardanoNodePrePkg (10.7.0) depend on
proto-lens-protobuf-types, which invokes protoc at build time through its
custom Setup.hs.  Upstream hydra (nix/hydra/project.nix) and upstream
cardano-node 10.7.0 (nix/haskell.nix) both inject pkgs.buildPackages.protobuf
into build-tools — this project was missing that module, causing all hydra and
cardano-node-pre builds to fail with "couldn't find the executable protoc".