fix(nix): Use correct platform for x86_64 cross-compilation

Signed-off-by: Steffen Vogel <[email protected]>

Author: stv0g

flake.nix

@@ -86,8 +86,13 @@
 
         # Cross-compiled packages
 
-        villas-node-x86_64-linux = if pkgs.system == "x86_64-linux" then pkgs.villas-node else pkgs.pkgsCross.x86_64-linux.villas-node;
-        villas-node-aarch64-linux = if pkgs.system == "aarch64-linux" then pkgs.villas-node else pkgs.pkgsCross.aarch64-multiplatform.villas-node;
+        villas-node-x86_64-linux =
+          if pkgs.system == "x86_64-linux" then pkgs.villas-node else pkgs.pkgsCross.gnu64.villas-node;
+        villas-node-aarch64-linux =
+          if pkgs.system == "aarch64-linux" then
+            pkgs.villas-node
+          else
+            pkgs.pkgsCross.aarch64-multiplatform.villas-node;
 
         dockerImage-x86_64-linux = pkgs.dockerTools.buildLayeredImage {
           name = "villas-node";