README: add note about MSYS2/Mingw64 environment

Signed-off-by: Hiroshi Miura <[email protected]>

README.rst

@@ -91,11 +91,19 @@ Same as usual, it can be installed with ``pip``:
 You are recommended to update pip before installing aqtinstall.
 
 .. note::
+
     aqtinstall depends several packages, that is required to download files from internet, and extract 7zip archives,
     some of which are precompiled in several platforms.
     Older pip does not handle it expectedly(see #230).
 
+.. note::
+
+    When you want to use it on MSYS2/Mingw64 environment, you need to set environmental variable
+    ``export SETUPTOOLS_USE_DISTUTILS=stdlib``, because of setuptools package on mingw wrongly
+    raise error ``VC6.0 is not supported``
+
 .. warning::
+
     There is an unrelated package `aqt` in pypi. Please don't confuse with it.
 
 It may be difficult to set up some Windows systems with the correct version of Python and all of ``aqt``'s dependencies.