After building successfully, you can modify the source (C/assembly) and rebuild a new ROM — that’s how custom hacks like SM64 Star Road or OoT Missing Link are made.
Here’s a draft for a post regarding — tailored for a community like GitHub, a forum (e.g., OoT or SM64 hacking), or a development blog. Title: Understanding baserom.us.z64 in N64 ROM Hacking baserom us z64
It’s a byte-for-byte copy of the original US version 1.0 ROM of the game. The decompilation process uses it as a reference to extract assets, verify matching code, and regenerate a fully compilable ROM. After building successfully, you can modify the source