build(nix): fix build of deltachat-rpc-server-x86_64-darwin

Author: link2xt

.github/workflows/nix.yml

@@ -95,10 +95,11 @@ jobs:
       matrix:
         installable:
           - deltachat-rpc-server
+          - deltachat-rpc-server-x86_64-darwin
 
-          # Fails to bulid
+          # Fails to build
+          # because of <https://github.com/NixOS/nixpkgs/issues/413910>.
           # - deltachat-rpc-server-aarch64-darwin
-          # - deltachat-rpc-server-x86_64-darwin
     steps:
       - uses: actions/checkout@v5
         with:

flake.nix

@@ -237,6 +237,9 @@
             auditable = false; # Avoid cargo-auditable failures.
             doCheck = false; # Disable test as it requires network access.
 
+            CARGO_TARGET_X86_64_APPLE_DARWIN_RUSTFLAGS = "-Clink-args=-L${pkgsCross.libiconv}/lib";
+            CARGO_TARGET_AARCH64_APPLE_DARWIN_RUSTFLAGS = "-Clink-args=-L${pkgsCross.libiconv}/lib";
+
             CARGO_BUILD_TARGET = rustTarget;
             TARGET_CC = "${pkgsCross.stdenv.cc}/bin/${pkgsCross.stdenv.cc.targetPrefix}cc";
             CARGO_BUILD_RUSTFLAGS = [