Allow sanitizer recovery

[jayvdb]

It is often useful to allow sanitizer recovery in order to see all errors instead of only the first.
This can be done with varying success using -DCMAKE_{}_FLAGS=-fsanitize-recover=all

Using input cmakeflags to add -DCMAKE_{}_FLAGS=-fsanitize-recover=all does not appear to work with these presets, as sanitizer presets already append -DCMAKE_{}_FLAGS.

The recipe should detect input cmakeflags setting -DCMAKE_{}_FLAGS and append its additions into the existing one rather than add another one.

But even with that fixed, IMO it would be good for the recipe here to allow adding -fsanitize-recover=all easily, or at least document how to do it.