tests: unskip empty_cross and future_util_multi_version

sample_projects/empty_cross/default.nix

@@ -1,52 +1,27 @@
-{ pkgs ? import ../../nix/nixpkgs.nix { config = { }; }
+{ pkgs ? import ../../nix/nixpkgs.nix { }
 , generatedCargoNix ? ./Cargo.nix { }
 }:
-
-let pkgs0 = pkgs; in
-
 let
-  pkgs = import pkgs0.path {
-    config = { };
-    crossSystem = {
+  # Create a new nixpkgs instance with crossSystem configured.
+  pkgsCross = import pkgs.path {
+    crossSystem = pkgs.lib.systems.elaborate {
       config = "riscv32-unknown-none-elf";
-      rustc = {
-        config = "riscv32i-unknown-none-elf";
-      };
+      rust.rustcTarget = "riscv32i-unknown-none-elf";
     };
   };
-  inherit (pkgs) lib;
-
-  instantiatedBuild = pkgs.callPackage generatedCargoNix {
-    defaultCrateOverrides = pkgs.defaultCrateOverrides;
-    buildRustCrateForPkgs = pkgs:
-      let
-        isBareMetal = pkgs.stdenv.hostPlatform.parsed.kernel.name == "none";
-        # Don't need other tools
-        stdenvBase = if isBareMetal then pkgs.stdenvNoCC else pkgs.stdenv;
 
-        stdenv =
-          if stdenvBase.hostPlatform.extensions ? sharedLibrary
-          then stdenvBase
-          else
-            lib.recursiveUpdate stdenvBase {
-              # This is used in buildRustCrate. Should probably be optional there.
-              hostPlatform.extensions.sharedLibrary = "";
-            };
+  instantiatedBuild = pkgsCross.callPackage generatedCargoNix {
+    buildRustCrateForPkgs = pkgsCross: pkgsCross.buildRustCrate.override {
+      # Don't need other tools for the crate and target in this test.
+      stdenv = pkgsCross.stdenvNoCC;
 
-        fun = pkgs.buildRustCrate.override {
-          inherit stdenv;
-
-          # Don't bother with cross compiler since we don't need stdlib
-          inherit (pkgs.buildPackages.buildPackages) rust rustc cargo;
-        };
-      in
-      args: fun (args // lib.optionalAttrs isBareMetal {
-        RUSTC_BOOTSTRAP = true;
-
-        # Needed for std for build.rs
-        nativeBuildInputs = args.nativeBuildInputs or [ ]
-          ++ lib.optional pkgs.stdenv.buildPlatform.isDarwin pkgs.buildPackages.libiconv;
-      });
+      # Don't bother with cross compiler since we don't need stdlib, this test only uses core.
+      inherit (pkgsCross.buildPackages.buildPackages) rustc cargo;
+    };
   };
 in
-instantiatedBuild.rootCrate.build
+instantiatedBuild.rootCrate.build.overrideAttrs {
+  # error[E0554]: `#![feature]` may not be used on the stable release channel
+  # Only needed for this test.
+  RUSTC_BOOTSTRAP = true;
+}

tests.nix

@@ -509,17 +509,13 @@ let
       name = "future_util_multi_version";
       src = ./sample_projects/future_util_multi_version;
       expectedOutput = "Hello, world!";
-      # FIXME: https://github.com/kolloch/crate2nix/issues/83
-      skip = true;
     }
 
     {
       name = "empty_cross";
       src = ./sample_projects/empty_cross;
       cargoToml = "Cargo.toml";
       customBuild = "sample_projects/empty_cross/default.nix";
-      # # FIXME: https://github.com/nix-community/crate2nix/issues/319
-      skip = true;
     }
   ];
   buildTestDerivationAttrSet =