Normally,
$ make
To build with debugging symbols,
$ make DEBUG=1
To build with the JIT off,
$ make JIT=0
Lastly, to verify your build,
$ make test
To build the bleeding edge, you will need make, binutils and gcc.
$ git clone git://github.com/fogus/potion.git
$ cd potion
$ make
Since Potion is only a single binary right now and there's no additional libs, I haven't written an installation step yet.
Potion's win32 binaries are built using MinGW. http://mingw.org/
It's a bit hard to setup mingw and make on Windows. I usually run a shell under Cygwin and add MinGW to my $PATH.
Once that's all done,
$ make
The easiest way to do this, actually, is on Linux.
On Ubuntu, if you have MinGW installed,
$ make CC=i586-mingw32msvc-gcc
You may then rename potion to potion.exe and
donate that binary to the needy.