Read http://mingw.org/wiki/Getting_Started and download mingw-get.
Then run:
mingw-get install gcc g++ mingw32-make mingw32-utils msys-core msys-m4 msys-bison msys-coreutils msys-diffutils msys-make
Don't forget to run msys.bat and from there:
/postinstall/pi.sh
Don't forget to add mingw\bin and mingw\msys\1.0\bin to %PATH%.
From http://sourceforge.net/projects/re2c download: re2c-0.13.5-bin.zip
re2c-0.13.5-bin.zip needs to be extracted to mingw/bin
Now, to compile the plugins you need to use the following command:
mingw32-make -f makefile COMMON=../path_to_common_from_far_svn
some plugins might need:
mingw32-make -f makefile COMMON=../path_to_common_from_far_svn/unicode
and some plugins might need:
mingw32-make -f makefile_gcc FARDEV=../path_to_far_svn_root
Some plugins might require the CRT (common/CRT) lib from Far repository, it can be built as follows:
mingw32-make -f makefile_lib_gcc
For x64 builds (not all plugins support it) use MingW64 from http://tdm-gcc.tdragon.net (and msys from above) and add DIRBIT=64 to all make commands.