Optimize Nix Logging and Suppress Compiler Noise

[szmyty]

🧹 Optimize Nix Logging and Suppress Compiler Noise

Summary

Nix is currently generating extremely verbose logs during builds (including thousands of GCC/Python/libmpdec warnings). This makes devcontainer builds noisy, slow, and difficult to debug. Nix provides configuration options to suppress these logs safely without hiding meaningful errors.

Tasks

• Create ${UBI_USER}’s Nix config directory:
  $HOME/.config/nix/nix.conf
• Add the following minimal recommended options:
  log-lines = 0 build-verbosity = 0
• Update the Dockerfile to append these settings after installing Nix:
  RUN mkdir -p $HOME/.config/nix && \ printf "log-lines = 0\nbuild-verbosity = 0\n" \ >> $HOME/.config/nix/nix.conf

Optional Enhancements

• Add Determinate Systems binary cache to prevent source builds (faster builds)
• Add GitHub-dependent binary caches for CI optimization
• Add a section to the UBI documentation explaining the Nix logging defaults

Acceptance Criteria

• Nix builds in the devcontainer show minimal output (errors only)
• No more GCC spam during Python or dependency builds
• Devcontainer logs become readable and significantly shorter
• Nix still surfaces real errors when they occur