[Toybox] fun with vfork

[David R. Hedges]

For what it's worth, your example (and the resulting symptom) seem to 
fall squarely in this undefined territory from the vfork manpage / POSIX 
description:
> the behavior is undefined if the process created by vfork() [..] calls 
> any other function before successfully calling [..] one of the exec(3) 
> family of functions

This doesn't solve your problem, but I wanted to make sure you're aware 
of (and deliberately chose to accept) that.