I did some more poking around with gdb, and was able to isolate one issue. When run outside of cygwin, `uv_guess_handle` returns `UV_UNKNOWN_HANDLE` such that `init_stdio_handle` errors out. When run inside of cygwin, `uv_guess_handle` returns `UV_NAMED_PIPE` to no ill effect.
How can this be? I'm hoping an expert knows. I opened an issue <https://github.com/JuliaLang/julia/issues/9244> for this.
