Log Message:
regress/tools: clarify that only the NetBSD 7 shell exhibits this bug

The test has been changed again to fail since making the test pass would
mean this bug could later silently show up inside a large GNU configure
script where it would be impossible to find. Therefore, when using pkgsrc
on NetBSD 7, it is better to switch to another shell for doing pkgsrc
work.

The comment has been updated to be more accurate.