SRE should fail more gracefully when SymbolWriter is missing

XA doesn't ship SymbolWriter and our SRE impl throws if you request that symbols be produced.

We should fail silently in this case and produce a warning.

It would be even better if we shipped a symbol writer for Android, thought that would have very limited value.


Reference: https://bugzilla.xamarin.com/show_bug.cgi?id=53038