buildRustCrate: make default value for codegenUnits configurable

, cargo

, jq

, libiconv

# Controls codegen parallelization for all crates.

# May be overriden on a per-crate level.

# See <https://doc.rust-lang.org/rustc/codegen-options/index.html#codegen-units>

, defaultCodegenUnits ? 1

}:

let

      colors = lib.attrByPath [ "colors" ] "always" crate;

      extraLinkFlags = lib.concatStringsSep " " (crate.extraLinkFlags or [ ]);

      edition = crate.edition or null;

      codegenUnits = if crate ? codegenUnits then crate.codegenUnits else 1;

      codegenUnits = if crate ? codegenUnits then crate.codegenUnits else defaultCodegenUnits;

      extraRustcOpts =

        lib.optionals (crate ? extraRustcOpts) crate.extraRustcOpts

          ++ extraRustcOpts_