build(macos): Add missing system packages for {conf-libffi,conf-zlib}

Author: erikmd

.ci-macosx.sh

@@ -40,6 +40,9 @@ brew install pkg-config
 brew install opam
 brew install libev
 brew install openssl
+brew install libffi
+brew install zlib
+
 opam init -y -a --bare
 
 opam switch create . ocaml-base-compiler --deps-only --locked -y -j 2 # -v

.github/workflows/static-builds.yml

@@ -100,6 +100,7 @@ jobs:
           brew install openssl@3  # Workaround https://github.com/ocaml/opam-repository/issues/19676
           brew install zstd  # Install zstd to avoid "ld: Undefined symbols: _ZSTD_*" at linking time
           # ^-> see also https://github.com/ocaml/ocaml/issues/12562
+          brew install libffi zlib  # needed since https://github.com/ocaml-sf/learn-ocaml/pull/610
           opam switch create . ocaml-base-compiler --deps-only
       - name: Build the binaries
         run: |