cross: split delfin fix into nixpkgs patch

overlays/cross.nix

@@ -138,10 +138,10 @@ in with final; {
     '';
   });
 
-  # 2025/08/26: upstreaming is unblocked
-  delfin = prev.delfin.override {
-    cargo = crossCargo;
-  };
+  # 2025/08/26: upstreaming is unblocked, on desko branch `pr-delfin-cross`
+  # delfin = prev.delfin.override {
+  #   cargo = crossCargo;
+  # };
 
   # 2025/07/27: upstreaming is unblocked
   # dtrx = prev.dtrx.override {

pkgs/by-name/nixpkgs-bootstrap/patches.nix

@@ -69,6 +69,13 @@ in
     hash = "sha256-b5BNpbM7lXSPT9h3zQZStPRk6yyfH4x6g2tpjXW94EM=";
   })
 
+  (fetchpatch' {
+    # desko nixpkgs branch: `pr-delfin-cross`
+    name = "delfin: fix cross compilation";
+    saneCommit = "b19145967431b49849d7dc5e0657322134297a24";
+    hash = "sha256-Zj2U5y94oapHGZ/Ez/5pM5MY3wAwt5jj5hht9xDSHx0=";
+  })
+
   (fetchpatch' {
     name = "coincurve: fix build";
     # saneCommit = "cd118a2491e613f0d4dd8673a6ac17a0094dd987";