rr-debugger/rr ? reverse-engineered prompt

Build me a lightweight Linux tool for recording and replaying program runs so I can debug them later, especially when a bug only happens once. I want it to work with gdb, and make reverse stepping and reverse continue feel smooth, so I can inspect what happened before a crash or bad state. It should handle normal user programs that launch child processes and threads, and it should be practical to build and run on modern Linux systems. Use the existing project structure here and make it compile cleanly, with clear instructions for building and testing. If you need to check current Linux or gdb details online, do that. I care most about the core record and replay flow, reliable debugging, and a simple command line experience that feels like a real developer tool.