- add `builder_is_windows`, `builder_is_macos` and `builder_is_linux`
functions
- add/move `BUILDER_OS` env variable to `resources/builder.inc.sh`
- use the new functions and env variable
Fixes: #14109
Test-bot: skip
- remove `builder_is_running_on_ci` function since there already is a
similar `builder_is_ci_build` function
- use `GITHUB_ACTIONS` environment variable instead of `GITHUB_RUN_ID`
to detect if we're run be GitHub Actions
This adds the three additional functions `builder_is_running_on_ci`,
`builder_is_running_on_docker`, and `builder_is_running_on_gha` to be
able to detect if the build is running in a CI or CI-like container
environment.
