stack setup does not use gcc specified with "with-gcc"

[BebeSparkelSparkel]

General summary/comments (optional)

expect to be able to specify the gcc path to be used with with-gcc in config.yaml and have stack setup --verbose use that version when adding a binary-dis of ghc.

Steps to reproduce

1. Ensure that there is a gcc version less than 4.4 in PATH. `

$ gcc --version
gcc (GCC) 4.2.1 20070719
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

2. Have a binary distribution on file and list it in config.yaml

# example config.yaml entry
setup-info:
  ghc:
    openbsd64-maj6-min7:
      8.8.1:
        url: '/home/user/ghc/ghc-8.8.1-x86_64-unknown-openbsd.tar.xz'

3. Add the with-gcc to config.yaml. Example with-gcc: '/usr/local/bin/egcc'
4. Create a new project stack new different-gcc-; cd different-gcc
5. Add compiler: ghc-8.8.1 to the project's stack.yaml
6. run stack setup --version

~/.stack/config.yaml

setup-info:
  ghc:
    openbsd64-maj6-min7:
      8.8.1:
        url: '/home/wjr/repos/ghc/ghc-8.8.1-x86_64-unknown-openbsd.tar.xz'
with-gcc: '/usr/local/bin/egcc'

different-gcc-version/stack.yaml

resolver: lts-14.27
compiler: ghc-8.8.1
packages:
- .

Expected

I expected stack to use the gcc specified with with-gcc when importing a new ghc distribution.

Actual

Stack continues to use the gcc that it finds in PATH

$ stack setup --verbose
...
2021-02-24 10:07:26.701864: [error] configure: error: Need at least gcc version 4.4 (4.7+ recommended)
2021-02-24 10:07:26.770883: [debug] checking version of gcc...
2021-02-24 10:07:26.773779: [error] Received ExitFailure 1 when running
Raw command: /home/wjr/.stack/programs/x86_64-openbsd/ghc-maj6-min7-8.8.1.temp/ghc-8.8.1/configure --prefix=/home/wjr/.stack/programs/x86_64-openbsd/ghc-maj6-min7-8.8.1/
Run from: /home/wjr/.stack/programs/x86_64-openbsd/ghc-maj6-min7-8.8.1.temp/ghc-8.8.1/

2021-02-24 10:07:26.773999: [error] 
Error: Error encountered while configuring GHC with
         /home/wjr/.stack/programs/x86_64-openbsd/ghc-maj6-min7-8.8.1.temp/ghc-8.8.1/configure --prefix=/home/wjr/.stack/programs/x86_64-openbsd/ghc-maj6-min7-8.8.1/
         run in /home/wjr/.stack/programs/x86_64-openbsd/ghc-maj6-min7-8.8.1.temp/ghc-8.8.1/
     
       The following directories may now contain files, but won't be used by stack:
         - /home/wjr/.stack/programs/x86_64-openbsd/ghc-maj6-min7-8.8.1.temp/
         - /home/wjr/.stack/programs/x86_64-openbsd/ghc-maj6-min7-8.8.1/
     
       For more information consider rerunning with --verbose flag
     
Configuring GHC ... 

Stack version

$ stack --version
Version 2.6.0, Git revision 30224e347624f34c9ebbbb444c07339cd123eb4d (8277 commits) PRE-RELEASE x86_64 hpack-0.33.0

Method of installation

stack install compile source