envp may be unreliable in global initializers

Hypothetical cause of BF-17563.

We clone the envp we got from main(argv,argc,env) into the InitializerContext.
I believe it may be corrupted by static initializers by the time main runs.
We can use environ instead. A better fix would be to change idiom so that InitializerContext provides a getenv accessor instead of a full snapshot of the environment. Nobody should need to see everything in the environment, they can pick out the keys they're interested in one by one. That's safer than a snapshot.