Added build container MAC address support

[TIR44]

Summary

• Added a pack build --mac-address flag and passed it through client.BuildOptions.ContainerConfig.
• Stored the parsed MAC address on lifecycle options and applied it to Docker NetworkingConfig.EndpointsConfig for the selected build container network.
• Kept the default path unchanged by only sending NetworkingConfig when a MAC address is configured.

Output

Before

pack build had no way to pass a MAC address to the build container network endpoint.

After

pack build --mac-address 01:23:45:67:89:ab ... validates the address and creates lifecycle containers with that MAC address on the configured network endpoint.

Documentation

• Should this change be documented?
  • Yes. The new CLI flag should be included in the generated command reference.

Related

Resolves #1779

Tests

• go test ./internal/build -run '^TestPhaseConfigProvider$' -count=1
• go test ./internal/commands -run '^TestBuildCommand$' -count=1
• go test ./pkg/client -run '^TestBuild$' -count=1
• go test ./internal/commands ./pkg/client -count=1
• make verify-format
• golangci-lint run -c golangci.yaml

GitHub checks passed on the latest commit (aa6408f): DCO, CodeQL, build tests on macOS/Linux/Windows, and compatibility acceptance combos.

I also tried go test ./internal/build ./internal/commands ./pkg/client -count=1; internal/commands and pkg/client passed, but the full internal/build package failed locally because Docker is not available at /var/run/docker.sock.

make lint initially failed locally because the pinned golangci-lint binary was built with Go 1.24 while this repo targets Go 1.25.10. Reinstalling the same pinned version with GOTOOLCHAIN=go1.25.10 and then running golangci-lint run -c golangci.yaml passed with 0 issues.