Fixed libsodium issue for windows build

default.nix

@@ -128,29 +128,32 @@ let
     )
   );
 
-in {
+  # For some reason the pkgsCross.pkgsStatic build of libsodium doesn't contain
+  # a `.a` file when compiled to a windows target, but rather contains
+  # a `.dll.a` file which libsodium-sys doesn't pick up on. Copying the one to
+  # the be the other seems to work.
+  libsodium = pkgs.runCommand "libsodium-wrapped" {
+    libsodium = pkgsCross.pkgsStatic.libsodium;
+  } ''
+    cp -rL "$libsodium" "$out"
+    chmod -R +w "$out"
+    if [ ! -e "$out"/lib/libsodium.a ] && [ -f "$out"/lib/libsodium.dll.a ]; then
+      cp "$out"/lib/libsodium.dll.a "$out"/lib/libsodium.a
+    fi
+  '';
 
-  inherit pkgs;
-
-  release = naersk.buildPackage rec {
-    inherit release;
-
-    src = ./.;
-    strictDeps = true;
-    doCheck = false;
-
-    depsBuildBuild = (buildTarget.depsBuildBuild pkgsCross) ++ [
+  buildEnv = rec {
+    nativeBuildInputs = (buildTarget.depsBuildBuild pkgsCross) ++ [
+      toolchain
       pkgs.protobuf
     ];
 
-    cargoBuildOptions = prev: prev++[
-      "--features=${builtins.concatStringsSep "," builtFeatures}"
-    ];
-
     OPENSSL_STATIC = "1";
     OPENSSL_LIB_DIR = "${pkgsCross.pkgsStatic.openssl.out}/lib";
     OPENSSL_INCLUDE_DIR = "${pkgsCross.pkgsStatic.openssl.dev}/include";
 
+    SODIUM_LIB_DIR = "${libsodium}/lib";
+
     # Required because ring crate is special. This also seems to have
     # fixed some issues with the x86_64-windows cross-compile :shrug:
     TARGET_CC = "${pkgsCross.stdenv.cc}/bin/${pkgsCross.stdenv.cc.targetPrefix}cc";
@@ -168,6 +171,24 @@ in {
     ];
   };
 
+in {
+
+  inherit pkgs pkgsCross;
+
+  release = naersk.buildPackage (rec {
+    inherit release;
+
+    src = ./.;
+    strictDeps = true;
+    doCheck = false;
+
+    cargoBuildOptions = prev: prev++[
+      "--features=${builtins.concatStringsSep "," builtFeatures}"
+    ];
+  } // buildEnv);
+
+  shell = pkgsCross.mkShell buildEnv;
+
   # TODO
   #clippy = {
   #  amd64 = (compile {