Currently glib obtains stdout of the parent process, then checks its type.
If stdout is a console, a console spawn helper is used.
Otherwise a non-console spawn helper is used.

While i won't pretend to know what the goal was, i do know that this logic
produces very inconvenient results when stdout is piped into a file.

If stdout is a file (i.e. not a console), the parent process does, in fact,
have a console attached, and the child is a console process too, then this
happens:
* Parent (console) checks stdout
* stdout is a file
* Parent spawns spawn-helper (non-console)
* Spawn helper (no console) does its job and spawns the child (console)
* Child is spawned. Since it's a console application, and it inherited
  no console from the helper, W32 creates a console for it.

This results in new, empty console window appearing on screen while the
child is alive. If the child is launched repeatedly (developer tools often
are) and is short-lived, the DE will be unusable while this is being done,
since it will have console windows appearing and disappearing rapidly.

The fix is to look for a console window and use its presence to decide which
helper to use. After all, I/O is completely independent of consoles, so the
only logical reason for two different helpers to exist is to avoid spawning
new console windows.