libs/wine: give user an error message if WINEARCH is not win32/win64 (try 2) (resend)

[Alex Henrie]

We need this in order to stop people from confusing themselves with
typos like "WINEARCH=wine64" instead of "WINEARCH=win64". To be
effective, the check has to be done before prefix creation, and
libs/wine/config.c is the most logical choice. We don't have to worry
here about whether WINEARCH=win64 is a valid option because not much
later dlls/ntdll/server.c prints an error message if WINEARCH=win64 but
the wineserver was only able to create a 32-bit prefix.

Signed-off-by: Alex Henrie <alexhenrie24 at gmail.com>