Add Torch 2.7 with ROCm 6.4 as a non-upstream variant

Author: danieldk

versions.nix

@@ -32,6 +32,14 @@
     systems = [ "x86_64-linux" ];
     upstreamVariant = true;
   }
+  {
+    torchVersion = "2.7";
+    rocmVersion = "6.4.2";
+    cxx11Abi = true;
+    systems = [ "x86_64-linux" ];
+    upstreamVariant = false;
+  }
+
   {
     torchVersion = "2.7";
     cxx11Abi = true;
@@ -77,7 +85,7 @@
   }
   {
     torchVersion = "2.8";
-    rocmVersion = "6.4.1";
+    rocmVersion = "6.4.2";
     cxx11Abi = true;
     systems = [ "x86_64-linux" ];
     upstreamVariant = true;