Fix Cargo mismatch on MacOS build

The flake.nix uses the default crane toolchain on darwin.
Override the default crane toolchain and specify the target
to use the correct rust toolchain.

.github/workflows/nix.yaml

@@ -103,6 +103,6 @@ jobs:
         uses: >- # v4
           DeterminateSystems/magic-nix-cache-action@fc6aaceb40b9845a02b91e059ec147e78d1b4e41
 
-      - name: Run build
-        run: >
-          nix build
+      - name: Test nix run
+        run: |
+           nix run -L .#nativelink-is-executable-test

flake.nix

@@ -87,7 +87,7 @@
 
         craneLib =
           if pkgs.stdenv.isDarwin
-          then crane.lib.${system}
+          then (crane.mkLib pkgs).overrideToolchain stable-rust.default
           else
             (crane.mkLib pkgs).overrideToolchain (stable-rust.default.override {
               targets = ["x86_64-unknown-linux-musl"];
@@ -138,6 +138,8 @@
 
         local-image-test = import ./tools/local-image-test.nix {inherit pkgs;};
 
+        nativelink-is-executable-test = import ./tools/nativelink-is-executable-test.nix {inherit pkgs nativelink;};
+
         generate-toolchains = import ./tools/generate-toolchains.nix {inherit pkgs;};
 
         native-cli = import ./native-cli/default.nix {inherit pkgs;};
@@ -197,7 +199,7 @@
           };
         };
         packages = rec {
-          inherit publish-ghcr local-image-test nativelink nativelink-debug native-cli lre-cc;
+          inherit publish-ghcr local-image-test nativelink-is-executable-test nativelink nativelink-debug native-cli lre-cc;
           default = nativelink;
 
           rbe-autogen-lre-cc = rbe-autogen lre-cc;
@@ -272,6 +274,7 @@
 
               # Additional tools from within our development environment.
               local-image-test
+              nativelink-is-executable-test
               generate-toolchains
               customClang
               native-cli

tools/nativelink-is-executable-test.nix

@@ -0,0 +1,27 @@
+{
+  pkgs,
+  nativelink,
+  ...
+}:
+pkgs.writeShellScriptBin "is-executable-test" ''
+  set -xuo pipefail
+
+  nativelink_output="$(${nativelink}/bin/nativelink 2>&1)"
+
+  print_error_output=$(cat <<EOF
+  error: the following required arguments were not provided:
+    <CONFIG_FILE>
+
+  Usage: nativelink <CONFIG_FILE>
+
+  For more information, try '--help'.
+  EOF)
+
+  if [ "$nativelink_output" = "$print_error_output" ]; then
+    echo "The output of nativelink matches the print_error output."
+  else
+    echo 'The output of nativelink does not match the print_error output:'
+    diff <(echo "$nativelink_output") <(echo "$print_error_output") >&2
+    exit 1
+  fi
+''