The default `STACK_ROOT` is `~/.stack` only on Unix-like operating systems. On Windows, the default is `%APPDATA%/stack` (usually `%HOME%\AppData\Roaming\stack`).
On Unix-like OSs, Stack stores GHC and other tools in a `programs` directory in the `STACK_ROOT`. On Windows, Stack stores those tools and MSYS2 in `%LOCALAPPDATA%\Programs\stack` (usually `%HOME%\AppData\Local\Programs\stack`).
