Description

Proxy options from config.json are not set as build args when using the classic builder (DOCKER_BUILTKIT=0).

Steps To Reproduce

1. Setup a simple compose project with a to-be-built image, which would need proxy environment variables at build-time

2. Have proxies set in config.json
3. Run docker-compose build
4. Observe that proxy environment variables are unset

2.16.0 still has args set:

2.17.0 (and 2.20.0) do not:

Compose Version

2.16.0 works, 2.17.0 & 2.20.0 do not work

Docker Environment

podman 4.4.1 with `DOCKER_BUILDKIT=0` and `DOCKER_HOST=<podman rootless socket>` set for compose to access the compat api

Anything else?

Support for config.json proxies to build args added in #10159

Since #10374 (released in 2.17.0) toBuildOptions seems to be no longer called in the if !buildkitEnabled code, and proxies are populated from config in that code.