FYI, I just proposed the following for MSYS (when launching "native" apps, like the MinGW binutils/gcc, or MSVC tools):
http://thread.gmane.org/gmane.comp.gnu.mingw.msys/4820 2010.09.04 Charles Wilson <...> * path.cc (msys_p2w): Support conversion of @file arguments. If we're lucky, it'll be in MSYS-1.0.16. -- Chuck