Stop trying to add APIs to mutate environment variables. It's not going to happen! There is no known way to mutate environment variables in a multithreaded Unix process without risk of native crashes (and I have worn the hat of poor support engineer trying to diagnose SEGV in getenv). IIRC we made the decision 13 years ago to cache the environment on first access, and that was before the thread-unsafety of putenv was fully appreciated.
Yes, Java still has a serious startup performance problem; that should be attacked more directly.
