[Mingw-cross-env-list] Issue with libboost_thread 1.44 static

[Lothar May]

Hi,

I'm currently trying to use your cross compiler and most things went
well so thanks for all your work! However, there is one known issue
with boost and mingw, if boost is built as static lib. A patch needs
to be applied to libboost_thread, otherwise there will be an error
when linking the app. See

https://svn.boost.org/trac/boost/ticket/4258

for the patch. Also (a note to developers), BOOST_THREAD_USE_LIB needs
to be defined when using static libboost_thread.

Thanks,
Lothar