pokeemerald/INSTALL.md

First, you must put a Pokémon Emerald (US) ROM in the root directory of the repository and name it baserom.gba. It should have a SHA1 checksum of f3ae088181bf583e55daf962a92bb46f4f1d07b7. Then, follow the OS-specific instructions below.

Linux

TBD

Windows

Install devkitARM.

Then download pokeruby-tools. Copy the tools/ folder with the compiled exes to the tools/ folder in your pokeemerald/ directory.

You can then build pokeemerald using make in the MSYS environment provided with devkitARM.