ghcup 8.6.4 base library compiled without -haddock support

Describe the bug After installing ghc-8.6.4 with ghcup, ghci experimental :doc command does not show documentation of functions from base.

I noted that ~/.ghcup/ghc/8.6.4/share/doc/ghc-8.6.4/html seems to be ok.

To Reproduce Steps to reproduce the behavior:

1. ghcup install 8.6.4
2. Run ghci and try :doc print; I can see the ... Try re-compiling with '-haddock' message instead of haddock documentation of print function.

It works with ghc-8.6.3 installed with ghcup.

System information Paste the output of ghcup debug-info and provide additional OS information, if missing.

ghcup debug-info
Script version: 0.0.7

Script variables:
  GHC install location:     /home/marcin/.ghcup/ghc
  Binary install location:  /home/marcin/.ghcup/bin
  Tarball cache location:   /home/marcin/.ghcup/cache
  Downloader:               curl --fail -O <url>
  Script update url:        https://raw.githubusercontent.com/haskell/ghcup/master/ghcup
  GHC download baseurl:     https://downloads.haskell.org/~ghc
  Meta download url         https://raw.githubusercontent.com/haskell/ghcup/master/.download-urls
  Meta download format      1
  Meta version url          https://raw.githubusercontent.com/haskell/ghcup/master/.available-versions
  Meta version format       1

Detected system information:
  Architecture:   x86_64
  Distribution:   Gentoo
  Distro alias:   unknown
  Distro version: