Use go mod cache mount for build

[jakub-id]

No description provided.

[Copilot]

Pull request overview

This PR optimizes Docker build performance by adding Go module cache mounts to the build steps in both the broker and illmock Dockerfiles. Previously, only the build cache (/root/.cache/go-build) was mounted during compilation, but now the module cache (/go/pkg/mod) is also mounted, allowing Go to reuse cached module artifacts during the build phase.

Changes:

• Add /go/pkg/mod cache mount to build steps in both Dockerfiles
• Update comment in broker/Dockerfile to reflect that both caches are now reused

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
illmock/Dockerfile	Add module cache mount to the go build command for the illmock binary
broker/Dockerfile	Add module cache mount to both go build commands (broker and archive binaries) and update comment to indicate both caches are reused