c4937ae9

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

Add debug mode and GHC heap limits to instrumented compilation

- Add `--debug` plugin option that prints each mutation site as it is
  recorded, so we can trace what the plugin is doing during instrumented
  compilation.
- Add `ghcMemLimit` parameter (default 16g) to `addManifest.nix` and
  `mutationCheck` in `mutation-checks.nix`; pass it to GHC via `-M`.
- Override Nix's default `-j16 -A64M` with `-j1 -A32M --disable-optimization`
  to prevent superlinear memory use when compiling instrumented code.
- Enable debug mode and set explicit memory limits in both e2e checks.
- Skip `Text.Colour.Chunk` (189 mutations) in the safe-coloured-text check:
  even at -O0 -j1 GHC needs >16g to compile that module.

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