Notes on adding non-Rust packages to fuel.nix in the future

[mitchmindtree]

The mkPackages function and patches.nix both make some assumptions based on the expectation that packages being built are Rust packages. This is fine for all fuel-core, sway and indexer packages, however these assumptions may need to be revisited if we aim to build non-Rust packages (e.g. NPM-based TS/JS stuff) in the future.

In order to enable building non-Rust packages, we should separate manifests by build process (e.g. buildRustPackage, buildNpmPackage, etc), either at the time of manifest creation, or by filtering them after their loaded using lists of names (e.g. one list of Rust package names, another list of NPM package names, etc).

E.g. the first condition under patches.nix should be revisited to ensure it is only applied for Rust-package manifests.