You need to setup the gcw0 buildroot first: Download a precompiled toolchain from http://www.gcw-zero.com/develop.

You need to cross-compile pixman.

Download Player and liblcf from GitHub:

git clone --depth=1 https://github.com/EasyRPG/Player.git
cd Player/libs
git clone --depth=1 https://github.com/EasyRPG/liblcf.git
cd ..

Change into the builds/opendingux folder and start the build:

cd builds/opendingux
make

If no error occured, there will be an EasyRPG executable in the gcw-zero subdirectory. To build an opk ready to deploy to the device:

cd gcw-zero
./opk_build.sh