Tuist Xcode cache for GitLab CI

Keep Xcode's compilation cache across jobs on Tuist macOS runners. Include the template and reference its snippet before your build commands:

include:
  - remote: https://raw.githubusercontent.com/tuist/xcode-cache-gitlab/v1/xcode-cache.yml

build:
  tags: [tuist-macos]
  before_script:
    - !reference [.tuist-xcode-cache, before_script]
  script:
    - xcodebuild build -scheme App COMPILATION_CACHE_ENABLE_CACHING=YES

Use !reference rather than extends: extends replaces before_script, so it cannot combine this snippet with the module cache's or your own. You can also vendor xcode-cache.yml and use include:local.

The snippet only decides where the cache lives. Turning compilation caching on stays with your project: set COMPILATION_CACHE_ENABLE_CACHING, or run tuist setup cache to share it through Tuist's remote cache. It points XCODE_XCCONFIG_FILE at a file with the cache's location and size limit; a XCODE_XCCONFIG_FILE the job already sets is included last, so its settings win.

Tuist does not yet verify GitLab jobs for its built-in caches, so on GitLab the cache starts empty and is not saved. Once Tuist verifies GitLab jobs, the same snippet starts saving with no pipeline change.

On runners that are not Tuist macOS runners the snippet does nothing. If the runner could not restore the cache, it warns and the job runs with an empty one; it never fails the job. SOURCE_COMMIT records its monorepo source.