Re #6675 Clarify effect of --no-install-ghc re MSYS2 on Windows

Author: mpilgrem

doc/configure/global_flags.md

@@ -144,9 +144,11 @@ version of its built-in Hpack library to the standard output stream (e.g.
 
 Default: Enabled
 
-Enables/disables the download and instalation of GHC if necessary. For further
-information, see the documentation for the corresponding non-project specific
-configuration [option](yaml/non-project.md#install-ghc).
+Enables/disables the download and installation of GHC when necessary. On
+Windows, `--no-install-ghc` also disables the download and installation of the
+Stack-supplied MSYS2 when necessary. For further information, see the
+documentation for the corresponding non-project specific configuration
+[option](yaml/non-project.md#install-ghc).
 
 ## `--jobs` or `-j` option
 

doc/configure/yaml/non-project.md

@@ -874,7 +874,9 @@ Default: `true`
 
 Command line equivalent (takes precedence): `--[no-]install-ghc` flag
 
-Whether or not to automatically install GHC when necessary.
+Whether or not to download and install GHC when necessary. On Windows,
+`install-ghc: false` also disables the download and installation of the
+Stack-supplied MSYS2 when necessary.
 
 ## jobs