haskell stack

stack struggles

With no local config present, `stack` is picking the old ghc 8.2.2:

```sh
➜  test stack ghci

Note: No local targets specified, so a plain ghci will be started with no package hiding or package options.
      
      You are using snapshot: lts-11.9
      
      If you want to use package hiding and options, then you can try one of the following:
      
      * If you want to start a different project configuration
        than /Users/dmitrizaitsev/.stack/global-project/stack.yaml, then you can use stack init to create a new stack.yaml for
        the packages in the current directory. 
        
      * If you want to use the project configuration
        at /Users/dmitrizaitsev/.stack/global-project/stack.yaml, then you can add to its 'packages' field.
      
Configuring GHCi with the following packages: 
GHCi, version 8.2.2: http://www.haskell.org/ghc/  :? for help
Loaded GHCi configuration from /private/var/folders/qg/f15r0d6s1gj6nsbg_517515h0000gn/T/haskell-stack-ghci/2a3bbd58/ghci-script
Prelude> 
```

However, my current ghc is 8.6.5:

```sh
➜  test ghci
GHCi, version 8.6.5: http://www.haskell.org/ghc/  :? for help
Loaded package environment from /Users/dmitrizaitsev/.ghc/x86_64-darwin-8.6.5/environments/default
Prelude> 
```

For some unclear reason, `stack` is instead referring to `lts-11.9`. But where is it defined? 

Here is my ~/.stack/config.yaml:

# This file contains default non-project-specific settings for 'stack', used
# in all projects.  For more information about stack's configuration, see
# http://docs.haskellstack.org/en/stable/yaml_configuration/
#
system-ghc: true