Stack install fails with linker errors when building system-filepath after update to 10.15 catalina

I have solved this by:

  1. uninstalling homebrew
  2. deleting ~/.stack
  3. cleaning out everything I could get my hands on in /usr/local
  4. reinstalling homebrew
  5. reinstalling stack from homebrew

I guess I will never know what precisely fixed this, but something did. Reinstalling stack was not previously enough.