add missing mcfgthreads windows build input on i686

default.nix

@@ -43,6 +43,7 @@ let
     stdenv = pkgs.stdenv;
     apple-sdk = if pkgs.stdenv.hostPlatform.isx86_64 then pkgs.apple-sdk_13 else pkgs.apple-sdk_14;
     installShellFiles = false;
+    windows = pkgs.windows;
     installShellCompletions = false;
     installManPages = false;
     notmuch = pkgs.notmuch;

package.nix

@@ -1,6 +1,7 @@
 { lib
 , pkg-config
 , rustPlatform
+, windows
 , fetchFromGitHub
 , stdenv
 , apple-sdk
@@ -37,6 +38,7 @@ rustPlatform.buildRustPackage rec {
 
   buildInputs = [ ]
     ++ lib.optional stdenv.hostPlatform.isDarwin apple-sdk
+    ++ lib.optional (stdenv.hostPlatform.isWindows && stdenv.hostPlatform.isi686) windows.mcfgthreads
     ++ lib.optional (builtins.elem "notmuch" buildFeatures) notmuch
     ++ lib.optional (builtins.elem "pgp-gpg" buildFeatures) gpgme;