I think you need to add apt-get update in order to get cmake to install. See this
image: gcc
before_script:
- apt-get update --yes
- apt-get install --yes cmake
build:
script:
- ./runner.sh
- ./bin/hello
In general, you can figure stuff out by jumping into the docker image to debug (in your case the image is the debian-based gcc:latest):
sudo docker run -it --rm gcc
If you had run your original apt-get install command inside the gcc container, you would have seen following error message that you could have then googled to figure out that apt-get update was needed
sudo docker run -it --rm gcc apt-get install --yes cmake
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package cmake is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'cmake' has no installation candidate
As this blog post mentions, you can do a test run locally by downloading the gitlab-runner executable:
gitlab-runner exec docker build
Running the gitlab-runner locally will have gitlab clone your repo and run through all the steps in the .gitlab-ci.yml and you can see the output and debug locally rather quickly.