Clarify and test the interaction of -with-rtsopts and -rtsopts flags
Looking at the user manual it's not clear how do
-rtsopts flags interact. I'd expect
-with-rtsopts to work even with
-rtsopts=ignoreAll, but I don't know if this is really the case, and because we don't have a way to print RTS flags (see #15261 (closed) for this) it's hard to make sure this works as expected.