configure: Detect MinGW-w64 Clang cross toolchain

[André Hentschel]

Am 30.12.2015 um 10:09 schrieb Alexandre Julliard:
> André Hentschel <nerv at dawncrow.de> writes:
> 
>> @@ -171,17 +171,19 @@ LIBS="$ac_wine_check_funcs_save_LIBS"])
>>  
>>  dnl **** Check for a mingw program, trying the various mingw prefixes ****
>>  dnl
>> -dnl Usage: WINE_CHECK_MINGW_PROG(variable,prog,[value-if-not-found],[path])
>> +dnl Usage: WINE_CHECK_MINGW_PROG(variable,progs,[value-if-not-found],[path])
>>  dnl
>>  AC_DEFUN([WINE_CHECK_MINGW_PROG],
>>  [case "$host_cpu" in
>>    i[[3456789]]86*)
>>      ac_prefix_list="m4_foreach([ac_wine_prefix],[w64-mingw32, pc-mingw32, mingw32msvc, mingw32],
>> -                        m4_foreach([ac_wine_cpu],[i686,i586,i486,i386],[ac_wine_cpu-ac_wine_prefix-$2 ]))
>> +                        m4_foreach([ac_wine_cpu],[i686,i586,i486,i386],
>> +                        m4_foreach([ac_wine_prog],[$2],[ac_wine_cpu-ac_wine_prefix-ac_wine_prog ])))
>>                          mingw32-$2" ;;
> 
> Do we need to duplicate all the names?  Or would it be sufficient to
> check only the w64-mingw one?
> 

It's possible to use clang with the classic MinGW.org
But if you still want to, I'd also reduce it to i686-w64-mingw32-clang and x86_64-w64-mingw32-clang,
because I think these are the most likely configurations. But then I'd avoid touching prog and would just append those to the list if that's what you want.
(Maybe we should drop the prog parameter all together?)