pythonPackages.kmsxx: fix build

gcc7 build fails with "internal compiler error", use gcc6 instead
by inheriting stdenv from pkgs.kmsxx

(cherry picked from commit 2c84e34)

pkgs/top-level/python-packages.nix

@@ -11930,7 +11930,11 @@ in {
   pika-pool = callPackage ../development/python-modules/pika-pool { };
   platformio = callPackage ../development/python-modules/platformio { };
 
-  kmsxx = callPackage ../development/libraries/kmsxx { };
+  kmsxx = (callPackage ../development/libraries/kmsxx {
+    inherit (pkgs.kmsxx) stdenv;
+  }).overrideAttrs (oldAttrs: {
+    name = "${python.libPrefix}-${pkgs.kmsxx.name}";
+  });
 
   pybase64 = callPackage ../development/python-modules/pybase64 { };