gitMinimal: fix build after PR #86848

In that case it specified $doc output but didn't even create it.
I expect it's better to do it this way instead of creating it
as an empty directory.
(Only the failed builds get rebuilt by this commit.)

pkgs/applications/version-management/git-and-tools/git/default.nix

@@ -36,7 +36,7 @@ stdenv.mkDerivation {
     sha256 = "0j685w6pzkn926z5nf5r8fij4ziipvw4c9yb0wc577nzf4j16rbd";
   };
 
-  outputs = [ "out" "doc" ];
+  outputs = [ "out" ] ++ stdenv.lib.optional withManual "doc";
 
   hardeningDisable = [ "format" ];