The only requirement for the ci system are the programs docker.io and bash. However, the mac cross build invokes curl on the host. Fix that.
Before:
$ FILE_ENV="./ci/test/00_setup_env_mac.sh" ./ci/test_run_all.sh
...
./ci/test/05_before_script.sh: line 22: curl: command not found
After:
... (command passes)