Fix build: handle missing ubuntu.sources for deb-src

[rollandf]

Check for the existence of /etc/apt/sources.list.d/ubuntu.sources before modifying it, falling back to /etc/apt/sources.list if needed. This fixes build failures on base images where the sources file location differs.

[greptile-apps]

Greptile Overview

Greptile Summary

This PR updates both Dockerfile and Dockerfile.nic-configuration-daemon to guard the deb-src enabling step by checking whether /etc/apt/sources.list.d/ubuntu.sources exists, and falling back to editing /etc/apt/sources.list when it doesn’t. This is intended to prevent build failures on base images that don’t ship the newer ubuntu.sources format, so apt-get source ... can proceed during image builds.

Confidence Score: 3/5

• This PR is mergeable once the deb-src fallback reliably enables source repos on minimal bases.
• The change is small and localized, but the new /etc/apt/sources.list fallback only uncomments existing deb-src lines; on images without any deb-src entries, apt-get source will still fail, which defeats the stated build-fix goal for some bases.
• Dockerfile, Dockerfile.nic-configuration-daemon

Important Files Changed

Filename	Overview
Dockerfile	Adds conditional logic to edit either ubuntu.sources or sources.list to enable deb-src before running apt-get update/install/source; fallback may still fail when sources.list lacks any deb-src entries.
Dockerfile.nic-configuration-daemon	Same conditional deb-src enabling logic as Dockerfile before apt-get source; fallback only uncomments existing deb-src lines and won’t help if none are present.

Sequence Diagram

sequenceDiagram
  participant Builder as Docker build
  participant FS as Base image filesystem
  participant APT as apt-get

  Builder->>FS: Check /etc/apt/sources.list.d/ubuntu.sources exists?
  alt ubuntu.sources present
    Builder->>FS: sed Types: deb -> Types: deb deb-src
  else ubuntu.sources absent
    Builder->>FS: Check /etc/apt/sources.list exists?
    alt sources.list present
      Builder->>FS: sed uncomment deb-src lines
    else sources.list absent
      Note over Builder,FS: No change to APT sources
    end
  end
  Builder->>APT: apt-get update
  Builder->>APT: apt-get install dpkg-dev...
  Builder->>APT: apt-get source dpkg-dev...

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[greptile-apps]

_{2 files reviewed, 2 comments}

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[greptile-apps]

deb-src enablement is incomplete

In the /etc/apt/sources.list fallback, this only uncomments existing deb-src lines (s/^#\s*deb-src/deb-src/). On images where deb-src entries are absent (common for minimal bases), this won’t enable source repos, and apt-get source ${PACKAGES} will still fail. If the goal is to reliably enable deb-src across bases, this branch likely needs to also add matching deb-src entries when none exist (or transform deb → deb-src lines) rather than only uncommenting.

[greptile-apps]

deb-src enablement is incomplete

Same as Dockerfile: the /etc/apt/sources.list fallback only uncomments pre-existing deb-src lines. If the base image’s sources.list doesn’t contain any deb-src entries, apt-get source ${PACKAGES} can still fail even though this block ran. Consider adding deb-src entries (or transforming corresponding deb lines) when no deb-src lines exist, instead of only uncommenting.