[WIP] Add `nix` to the projects (with Ubuntu packages)

[Pamplemousse]

:warning: This is a Work-In-Progress that does not even work (yet?) :warning:

As I am struggling to integrate nix to OSS-fuzz, these PR (with google/oss-fuzz#6317) helps to keep track of the progress, and help gather feedback on approaches taken.

Context

As part of a fellowship, I work on fuzzing nix; More details on https://discourse.nixos.org/t/tweag-fellowship-fuzzing-nix-0 . One of the "end-goal" of the project is to integrate nix to OSS-fuzz; This PR is a step in that direction.

Approach

Unlike google/oss-fuzz#6317 ;

This approach aims to stay close to OSS-fuzz's philosophy:

• use Docker for build-time reproducibility
• compile the fuzzers statically While still:
• leverage upstream's autotools system:
  • build nix libraries without hassle
  • add compilation of fuzz target
  • add extra flags to libraries (relies on nixos/nix#5175) for better fuzzer coverage and sanitization

Disadvantage: Doesn't work (yet); Dockerfile and build.sh are non trivial and will be a pain to maintain.

TODO

• [ ] :warning: correct the runtime SEGFAULT...
• [x] apply sanitizers to libraries
• [ ] don't clone a fork:
  • [ ] integrate fuzz targets upstream
  • [ ] integrate local.mk upstream
• [ ] compile and test coverage binary(ies)
• [ ] add auto_ccs to projects.yaml if maintainers are OK
• [x] sign the google-cla thing

cc @regnat

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[Pamplemousse]

@googlebot I signed it!