[flashrom] Building on Windows with mingw

[Miklos Marton]

Hello all,

I have tried to build the flashrom with mingw on Windows, but the build 
process fails with:

flash.h:336:1: error: '__MINGW_PRINTF_FORMAT' is an unrecognized format 
function
  type [-Werror=format=]
  __attribute__((format(__MINGW_PRINTF_FORMAT, 2, 3)));

I have checked the stdio.h shipped with the mingw installation, but it 
does not contains the __MINGW_PRINTF_FORMAT macro.

I have used the latest available mingw-get-setup, because the 20110530 
version (which mentioned in the wiki as known t obe working) segfaults 
when I select the MSYS Basic System feature.

I can build with WARNERROR=no, but some more permanent fix 
recommentation would be warmly welcome!