[distcc] building gcc for mingw requires a patch

[Daniel Kegel]

Someone recently said that using gcc and distccd on cygwin
worked fine for small apps, but crashed sometimes compiling larger things.
During that discussion, someone asked whether one could just
compile gcc to run on mingw to avoid possible cygwin problems.
For reference, here's a link to the gcc bug report about this being hard;
it contains a link to the latest patch that fixes collect2 so it runs on mingw.
   http://gcc.gnu.org/PR14316
- Dan