ghcup installs 8.8.3 just to warn about 8.10.1 being available

As in title. I believe the latest version should be installed, or there should at least be an option to specify the version manually by setting, say, BOOTSTRAP_HASKELL_GHC_VERSION. Ideally both would be true.

Cheers! :)

Relevant part of the log:

13:38 $ curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | BOOTSTRAP_HASKELL_NONINTERACTIVE='true' sh

<SNIP/>

[ Info  ] downloading: https://downloads.haskell.org/~ghc/8.8.3/ghc-8.8.3-x86_64-fedora27-linux.tar.xz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  193M  100  193M    0     0  3637k      0  0:00:54  0:00:54 --:--:-- 3353k
[ Info  ] verifying digest of: ghc-8.8.3-x86_64-fedora27-linux.tar.xz
[ Info  ] Unpacking: ghc-8.8.3-x86_64-fedora27-linux.tar.xz to /tmp/ghcup-IbOJmd
[ Info  ] Installing GHC (this may take a while)
[ Info  ] GHC installation successful
[ Warn  ] New GHC version available: 8.10.1. To upgrade, run 'ghcup install 8.10.1'
[ Info  ] GHC 8.8.3 successfully set as default version
[ Warn  ] New GHC version available: 8.10.1. To upgrade, run 'ghcup install 8.10.1'

<SNIP/>

Full log below

13:38 $ curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | BOOTSTRAP_HASKELL_NONINTERACTIVE='true' sh

Welcome to Haskell!

This script will download and install the following binaries:
  * ghcup - The Haskell toolchain installer (for managing GHC/cabal versions)
  * ghc   - The Glasgow Haskell Compiler
  * cabal - The Cabal build tool

ghcup installs only into the following directory, which can be removed anytime:
  /home/artur/.ghcup

[ Info  ] Upgrading GHCup...
[ Warn  ] No GHCup update available

System requirements 
  Note: You need the following packages: curl g++ gcc gmp make ncurses realpath xz-utils. Consult your distro documentation on the exact names of those packages.

[ Info  ] downloading: https://downloads.haskell.org/~ghc/8.8.3/ghc-8.8.3-x86_64-fedora27-linux.tar.xz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  193M  100  193M    0     0  3637k      0  0:00:54  0:00:54 --:--:-- 3353k
[ Info  ] verifying digest of: ghc-8.8.3-x86_64-fedora27-linux.tar.xz
[ Info  ] Unpacking: ghc-8.8.3-x86_64-fedora27-linux.tar.xz to /tmp/ghcup-IbOJmd
[ Info  ] Installing GHC (this may take a while)
[ Info  ] GHC installation successful
[ Warn  ] New GHC version available: 8.10.1. To upgrade, run 'ghcup install 8.10.1'
[ Info  ] GHC 8.8.3 successfully set as default version
[ Warn  ] New GHC version available: 8.10.1. To upgrade, run 'ghcup install 8.10.1'
[ Info  ] downloading: https://downloads.haskell.org/~cabal/cabal-install-3.2.0.0/cabal-install-3.2.0.0-x86_64-unknown-linux.tar.xz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 4260k  100 4260k    0     0  3163k      0  0:00:01  0:00:01 --:--:-- 3163k
[ Info  ] verifying digest of: cabal-install-3.2.0.0-x86_64-unknown-linux.tar.xz
[ Info  ] Unpacking: cabal-install-3.2.0.0-x86_64-unknown-linux.tar.xz to /tmp/ghcup-jaJGKg
[ Info  ] Installing cabal
[ Info  ] Cabal installation successful
Downloading the latest package list from hackage.haskell.org
To revert to previous state run:
    cabal v2-update 'hackage.haskell.org,2020-06-12T11:20:41Z'

Installation done!