Last, but not least, there's always a chance that somebody tries to exec
a Cygwin process from the /bin directory of another Cygwin installation.
This will result in loading "the other" Cygwin DLL for the child
process. Tricky, given that this requires process interaction, while
the whole idea of the change is to avoid interaction. So this case is
still not supported and the result is not determined. It might work,
but you can also easily see the friendly "multiple Cygwin" error message
instead. The rule is, keep separate Cygwin installations separate.