Doesn't yet work in 64bit cygwin! This is what you would do if it did work in 64 bit cygwin!
Attempt to compile Mercury on this computer?
So there may be problems for 64 bit Cygwin. You'll need to test it out. You have to use ROTD. http://dl.mercurylang.org/index.html
Extract the archive to a directory.
Mercury has a lot of dependencies. I'm running this after I've installed all the other things. So the only thing extra is flex at the moment. The configure command should tell you the rest.
apt-cyg install flex
apt-cyg install bison
configure --prefix "/cygdrive/c/Users/CMCDragonkai/mercury"
make PARALLEL=-j2
make PARALLEL=-j2 install
make clean