FF_USE_FASTZIP=1 is not respected when extracting cache

Summary

Setting FF_USE_FASTZIP=1 should make gitlab-runner use fastzip. This works when doing it from commandline (gitlab-runner cache-extractor ...), but it doesn't work when gitlab-runner is executed from Gitlab CI.

Steps to reproduce

Set following variable in .gitlab-ci.yml

variables:
  FF_USE_FASTZIP: 1

Add

environment = ["FF_USE_FASTZIP=1"]

in [[runners]] section of config.toml.

Each of those two above (tested separately) do propagate to CI jobs, i.e. printenv shows proper value. However they have no influence how cache is extracted during Gitlab CI job run.

Actual behavior

FF_USE_FASTZIP=1 in .gitlab-ci.yml or in config.toml has no influence on cache extraction.

Expected behavior

FF_USE_FASTZIP=1 in .gitlab-ci.yml or in config.toml should speed up cache extraction.

Relevant logs and/or screenshots

job log

[0KRunning with gitlab-runner 13.8.0 (HEAD)
[0;m[0K  on zm vxs2hc2x
[0;msection_start:1612310600:prepare_executor
[0K[0K[36;1mPreparing the "docker" executor[0;m
[0;m[0KUsing Docker executor with image zephyrprojectrtos/ci:v0.11.13 ...
[0;m[0KPulling docker image zephyrprojectrtos/ci:v0.11.13 ...
[0;m[0KUsing docker image sha256:53fd109ce6ebf138576a9a3276b7cb81a2e6a7776b304835a56d3fb6c45f7e36 for zephyrprojectrtos/ci:v0.11.13 with digest zephyrprojectrtos/ci@sha256:391bc7003d7c4e61b281d533c9c1066e5da8a1c9aade50f4d416dd1375570c56 ...
[0;msection_end:1612310603:prepare_executor
[0Ksection_start:1612310603:prepare_script
[0K[0K[36;1mPreparing environment[0;m
[0;mRunning on runner-vxs2hc2x-project-97-concurrent-0 via zm...
section_end:1612310603:prepare_script
[0Ksection_start:1612310603:get_sources
[0K[0K[36;1mGetting source from Git repository[0;m
[0;m[32;1mSkipping Git repository setup[0;m
[32;1mSkipping Git checkout[0;m
[32;1mSkipping Git submodules setup[0;m
section_end:1612310603:get_sources
[0Ksection_start:1612310603:restore_cache
[0K[0K[36;1mRestoring cache[0;m
[0;m[32;1mChecking cache for west-modules...[0;m
cache.zip is up to date                           [0;m 
[32;1mSuccessfully extracted cache[0;m
section_end:1612310619:restore_cache
...

Environment description

config.toml contents

concurrent = 4
check_interval = 0

[session_server]
  session_timeout = 1800

[[runners]]
  name = "zm"
  url = "https://gitlab.secret.site"
  token = "secret"
  executor = "docker"
  environment = ["FF_USE_FASTZIP=1"]
  [runners.custom_build_dir]
  [runners.cache]
    Type = "s3"
    Shared = true
    [runners.cache.s3]
      ServerAddress = "172.17.0.1:9000"
      AccessKey = "secret"
      SecretKey = "secret"
      BucketName = "gitlab-cache"
      Insecure = true
    [runners.cache.gcs]
    [runners.cache.azure]
  [runners.docker]
    tls_verify = false
    image = "ubuntu:20.04"
    privileged = false
    disable_entrypoint_overwrite = false
    oom_kill_disable = false
    disable_cache = false
    volumes = ["/cache"]
    shm_size = 0

Used GitLab Runner version

Version:      13.8.0
Git revision: HEAD
Git branch:   HEAD
GO version:   go1.15.7
Built:        unknown
OS/Arch:      linux/amd6

Possible fixes

I suspect that environment variables are not propagated when gitlab-runner cache-extractor ... is executed in docker executor. This is my gut feeling.