Yeah I think that might be helpful, I would appreciate that thank you 🙂

Hmm. It might not be what you're looking for... I never actually needed to compile or install kotlin. The image mentioned in line 1 contains preinstalled android-sdk with accepted licenses, etc.

image: <http://registry.gitlab.com/XXX|registry.gitlab.com/XXX>

variables:
  ANDROID_COMPILE_SDK: "27"
  ANDROID_BUILD_TOOLS: "27.0.3"
  CI_SERVER: "true"
    
stages:
    - build
    - test
    - upload

before_script:
 - export GRADLE_USER_HOME=`pwd`/.gradle

cache: 
  paths:
    - .gradle/wrapper
    - .gradle/caches

build:
  stage: build
  only:
    - master
    - gitlab_unit_tests
  script:
    - chmod +x ./gradlew
    - ./gradlew -g /cache --stacktrace app:assembleDevBackendDebug
  artifacts:
    paths:
    - app/build/outputs
  tags:
    - docker
    - multidex

...

Hmm that part is interesting, thanks for sharing this. I wonder what gradle is doing when it handles the dependency

I just checked the Dockerfile, there's no mention of kotlin. The only thing relevant is setting up https://dl.google.com/android/repository/sdk-tools-linux-3859397.zip and using sdkmanager to get platform tools and build tools, but that's no different from building with java written apps.