Compiler Explorer's CI infrastructure

Used to build our compilers, both ad hoc and on a regular basis. Uses https://github.com/github-aws-runners/terraform-aws-github-runner to script up some custom GH Actions runners that run on our infrastructure on demand, and scale back to zero when they're done. Our runners have access to the CE environment and they are mostly set up by the infra repo.

To deploy:

The webhook and secret should be the same every time, but they go in https://github.com/organizations/compiler-explorer/settings/apps/compiler-explorer-ci. If you need to output them you need to specifically ask them to be output as they are sensitive secret values, shared with GitHub only:

$ terraform output webhook

Make any changes in the ./packer directory, as needed.
Then run the appropriate build scripts:
- ./build-image.sh (x64 standard Linux runners)
- ./build-image-arm64.sh (ARM64 Linux runners)
- ./build-image-lin-builder.sh (Linux x64 library builder runners)
- ./build-image-win-builder.sh (Windows builder runners)
Once built you'll need to rerun the terraform apply. I recommend you terraform plan and review that, then apply the plan after it looks good.

Find the package in https://github.com/github-aws-runners/terraform-aws-github-runner/releases
- check for any incompatibilities compared to the current version
update the version in lambdas-download/main.tf
terraform apply in lambdas-download
update the version in main.tf
terraform init in toplevel and terraform apply. I recommend you terraform plan and review that, then apply the plan after it looks good.

update the runner_version in:
- packer-vars.hcl (x64 standard Linux and x64 library builder)
- packer-vars-arm64.hcl (ARM64 Linux)
- packer-vars-win-builder.hcl (Windows builder)
update the packer images (see above)