nix: disable big-parallel for aws-sdk-cpp

aws-sdk-cpp only takes ~1m52s on a 4 core machine under 50% load
which does not justify the requirement on big parallel.

Tested with `nix-build -A nixVersions.nix_2_6.aws-sdk-cpp`.

pkgs/tools/package-management/nix/common.nix

@@ -205,7 +205,7 @@ stdenv.mkDerivation {
   };
 
   passthru = {
-    inherit boehmgc;
+    inherit aws-sdk-cpp boehmgc;
 
     perl-bindings = perl.pkgs.toPerlModule (callPackage ./nix-perl.nix { inherit src version;  });
   };

pkgs/tools/package-management/nix/default.nix

@@ -24,6 +24,9 @@ let
     customMemoryManagement = false;
   }).overrideDerivation (args: {
     patches = (args.patches or [ ]) ++ [ ./patches/aws-sdk-cpp-TransferManager-ContentEncoding.patch ];
+
+    # only a stripped down version is build which takes a lot less resources to build
+    requiredSystemFeatures = null;
   });
 
   common = args: