stdenv: linux, darwin: don't build documentation for the the intermediate stages

For the cc of the intermediate stages, to be precise. Doing the same for
bintools requires lots of refactoring.

This is mainly for the future extensibility as now you can change
documentation generation with impunity without rebuilding the
whole of stdenv.

pkgs/stdenv/darwin/default.nix

@@ -86,6 +86,7 @@ in rec {
         extraPackages = lib.optional (libcxx != null) libcxx;
 
         nativeTools  = false;
+        propagateDoc = false;
         nativeLibc   = false;
         inherit buildPackages coreutils gnugrep bintools;
         libc         = last.pkgs.darwin.Libsystem;

pkgs/stdenv/linux/default.nix

@@ -89,6 +89,7 @@ let
              then null
              else lib.makeOverridable (import ../../build-support/cc-wrapper) {
           nativeTools = false;
+          propagateDoc = false;
           nativeLibc = false;
           buildPackages = lib.optionalAttrs (prevStage ? stdenv) {
             inherit (prevStage) stdenv;