PTY occasionally gets write errors with parallel make
Sometimes, when using the new PTY interceptor, I see an error from make (only during parallel builds) where there is a write error to stdout.
After some instrumentation on ptyintercept.c, it doesn't appear we're closing any FDs. I also increased our buffer sizes, but that had little-or-no effect.
The VTE test program I made doesn't seem to exhibit the behavior. I'm not sure if we're just very timing sensitive or what.