No, I didn't get any such warning with either graphical IDE or command line
compiler.  Remember, ISE_LIBRARY was defined when I built estudio and then
was not defined when I ran the Eiffel compiler, which might be different than
a "change of environment variable value".

Also, if I did get a warning in such a case, it seems that I would always
get VD80 warnings for every build of EiffelStudio, since (at least when I
build it) ISE_LIBRARY is always set to a value that will be different from
ISE_EIFFEL when estudio is installed.