cuda-modules: don't use *Platform attributes from pkgs

For more information about *why* this is desirable, see
https://github.com/NixOS/nixpkgs/pull/45717
and
https://github.com/NixOS/nixpkgs/issues/27069

pkgs/development/cuda-modules/cuda-library-samples/extension.nix

@@ -1,5 +1,12 @@
-{ hostPlatform, lib }:
+{
+  lib,
+  # NOTE: We would use backendStdenv to get the hostPlatform, but it's not available in the callPackage context
+  # we're using to call this file.
+  stdenv,
+}:
 let
+  inherit (stdenv) hostPlatform;
+
   # Samples are built around the CUDA Toolkit, which is not available for
   # aarch64. Check for both CUDA version and platform.
   platformIsSupported = hostPlatform.isx86_64 && hostPlatform.isLinux;

pkgs/development/cuda-modules/cuda-samples/extension.nix

@@ -1,7 +1,9 @@
 {
   cudaVersion,
-  hostPlatform,
   lib,
+  # NOTE: We would use backendStdenv to get the hostPlatform, but it's not available in the callPackage context
+  # we're using to call this file.
+  stdenv,
 }:
 let
   cudaVersionToHash = {
@@ -23,6 +25,8 @@ let
     "12.3" = "sha256-fjVp0G6uRCWxsfe+gOwWTN+esZfk0O5uxS623u0REAk=";
   };
 
+  inherit (stdenv) hostPlatform;
+
   # Samples are built around the CUDA Toolkit, which is not available for
   # aarch64. Check for both CUDA version and platform.
   cudaVersionIsSupported = cudaVersionToHash ? ${cudaVersion};

pkgs/development/cuda-modules/cutensor/extension.nix

@@ -15,9 +15,11 @@
 {
   cudaVersion,
   flags,
-  hostPlatform,
   lib,
   mkVersionedPackageName,
+  # NOTE: We would use backendStdenv to get the hostPlatform, but it's not available in the callPackage context
+  # we're using to call this file.
+  stdenv,
 }:
 let
   inherit (lib)
@@ -29,6 +31,8 @@ let
     trivial
     ;
 
+  inherit (stdenv) hostPlatform;
+
   redistName = "cutensor";
   pname = "libcutensor";
 

pkgs/development/cuda-modules/flags.nix

@@ -7,7 +7,9 @@
   cudaForwardCompat ? (config.cudaForwardCompat or true),
   lib,
   cudaVersion,
-  hostPlatform,
+  # NOTE: We cannot refer to backendStdenv as flags exists outside the fixed-point;
+  # otherwise, we would use that to get the hostPlatform.
+  stdenv,
   # gpus :: List Gpu
   gpus,
 }:
@@ -20,6 +22,8 @@ let
     trivial
     ;
 
+  inherit (stdenv) hostPlatform;
+
   # Flags are determined based on your CUDA toolkit by default.  You may benefit
   # from improved performance, reduced file size, or greater hardware support by
   # passing a configuration based on your specific GPU environment.

pkgs/development/cuda-modules/generic-builders/manifest.nix

@@ -10,7 +10,6 @@
   markForCudatoolkitRootHook,
   flags,
   stdenv,
-  hostPlatform,
   # Builder-specific arguments
   # Short package name (e.g., "cuda_cccl")
   # pname : String
@@ -40,6 +39,8 @@ let
     sourceTypes
     ;
 
+  inherit (backendStdenv) hostPlatform;
+
   # Get the redist architectures for which package provides distributables.
   # These are used by meta.platforms.
   supportedRedistArchs = builtins.attrNames featureRelease;
@@ -48,7 +49,7 @@ let
   # It is `"unsupported"` if the redistributable is not supported on the target platform.
   redistArch = flags.getRedistArch hostPlatform.system;
 
-  sourceMatchesHost = flags.getNixSystem redistArch == stdenv.hostPlatform.system;
+  sourceMatchesHost = flags.getNixSystem redistArch == hostPlatform.system;
 in
 backendStdenv.mkDerivation (finalAttrs: {
   # NOTE: Even though there's no actual buildPhase going on here, the derivations of the

pkgs/development/cuda-modules/generic-builders/multiplex.nix

@@ -3,7 +3,9 @@
   lib,
   cudaVersion,
   flags,
-  hostPlatform,
+  # NOTE: We would use backendStdenv to get the hostPlatform, but it's not available in the callPackage context
+  # we're using to call this file (cudaPackages.callPackage).
+  stdenv,
   # Expected to be passed by the caller
   mkVersionedPackageName,
   # pname :: String
@@ -40,6 +42,8 @@ let
     strings
     ;
 
+  inherit (stdenv) hostPlatform;
+
   evaluatedModules = modules.evalModules {
     modules = [
       ../modules

pkgs/development/cuda-modules/tensorrt/fixup.nix

@@ -1,7 +1,7 @@
 {
+  backendStdenv,
   cudaVersion,
   final,
-  hostPlatform,
   lib,
   mkVersionedPackageName,
   package,
@@ -17,6 +17,7 @@ let
     strings
     versions
     ;
+  inherit (backendStdenv) hostPlatform;
   # targetArch :: String
   targetArch = attrsets.attrByPath [ hostPlatform.system ] "unsupported" {
     x86_64-linux = "x86_64-linux-gnu";