Remove Torch source builds (#347)

Wheel builds have been working very well for us during the Torch 2.9
cycle and since 2.10 we also have support for RCs. Let's remove
from-source Torch builds completely to reduce the maintenance burden.

Author: danieldk

lib/build-sets.nix

@@ -33,7 +33,7 @@ let
         python-self: python-super: with python-self; {
           torch =
             if sourceBuild then
-              python-self."torch_${flattenVersion torchVersion}"
+              throw "Torch versions with `sourceBuild = true` are not supported anymore"
             else
               python-self."torch-bin_${flattenVersion torchVersion}";
         }

overlay.nix

@@ -29,14 +29,6 @@ in
     }
   );
 
-  magma = (prev.callPackage ./pkgs/magma { }).magma;
-
-  magma-hip =
-    (prev.callPackage ./pkgs/magma {
-      cudaSupport = false;
-      rocmSupport = true;
-    }).magma;
-
   nvtx = final.callPackage ./pkgs/nvtx { };
 
   metal-cpp = final.callPackage ./pkgs/metal-cpp { };
@@ -127,14 +119,6 @@ in
           xpuPackages = final.xpuPackages_2025_3;
         };
 
-        torch_2_8 = callPackage ./pkgs/python-modules/torch/source/2_8 {
-          xpuPackages = final.xpuPackages_2025_1;
-        };
-
-        torch_2_9 = callPackage ./pkgs/python-modules/torch/source/2_9 {
-          xpuPackages = final.xpuPackages_2025_2;
-        };
-
         triton-xpu_2_8 = callPackage ./pkgs/python-modules/triton-xpu {
           torchVersion = "2.8";
           xpuPackages = final.xpuPackages_2025_1;