Merge branch 'master' into staging

Compare to Hydra nixpkgs job 1260021.

pkgs/build-support/buildenv/default.nix

@@ -49,8 +49,11 @@ runCommand name
     pkgs = builtins.toJSON (map (drv: {
       paths =
         # First add the usual output(s): respect if user has chosen explicitly,
-        # and otherwise use `meta.outputsToInstall` (guaranteed to exist by stdenv).
-        (if (drv.outputUnspecified or false)
+        # and otherwise use `meta.outputsToInstall`. The attribute is guaranteed
+        # to exist in mkDerivation-created cases. The other cases (e.g. runCommand)
+        # aren't expected to have multiple outputs.
+        (if drv.outputUnspecified or false
+            && drv.meta.outputsToInstall or null != null
           then map (outName: drv.${outName}) drv.meta.outputsToInstall
           else [ drv ])
         # Add any extra outputs specified by the caller of `buildEnv`.

pkgs/build-support/replace-dependency.nix

@@ -61,7 +61,7 @@ let
   drvName = drv:
     discard (substring 33 (stringLength (builtins.baseNameOf drv)) (builtins.baseNameOf drv));
 
-  rewriteHashes = drv: hashes: runCommand (drvName drv) { nixStore = "${nix}/bin/nix-store"; } ''
+  rewriteHashes = drv: hashes: runCommand (drvName drv) { nixStore = "${nix.out}/bin/nix-store"; } ''
     $nixStore --dump ${drv} | sed 's|${baseNameOf drv}|'$(basename $out)'|g' | sed -e ${
       concatStringsSep " -e " (mapAttrsToList (name: value:
         "'s|${baseNameOf name}|${baseNameOf value}|g'"