GitLab CI Docker Runner (macos): chmod cannot access './gradlew': No such file or directory

I have been trying to setup GitLab CI with a Docker Runner installed on a macOS device to handle testing on my Android project. The Docker is installed and running on the Mac and Gitlab will start the job but fails at the build stage with the error

chmod: cannot access './gradlew': No such file or directory ERROR: Job failed: exit code 1

I have tried both the Android template .yml file included in GitLab CI as well as others found online with my current .yml configuration being:

image: jerbob92/gitlab-ci-android:latest

before_script:
    - export GRADLE_USER_HOME=`pwd`/.gradle
    - mkdir -p $GRADLE_USER_HOME
    - chmod +x ./gradlew

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

build:
  stage: build
  script:
     - ./gradlew assemble

test:
  stage: test
  script:
     - ./gradlew check

No matter what configuration I use the Runner fails during the chmod +x ./gradlew step. Is there a step I am missing here?