There used to be an internal flag '-XDenableSunApiLintControl' to enable using -Xlint to control them, but it was removed as part of a cleanup of 'unused options' in JDK-8148808.

This enhancement proposes restoring the ability to control sunapi as a lint category, including with -Xlint: and @SuppressWarnings.

Making sunapi mandatory and unsuppressible may have been a deliberate choice to encourage users to migrate off the deprecated APIs instead of suppressing. (I don't know the history of that decision or JDK-8148808, clarifications on that are welcome.) However in practice, due to bug JDK-8349846 sunapi diagnostics can be suppressed by passing -XDignore.symbol.file or some values of --system, so there is a suppression mechanism, it's just an ad-hoc one.

Providing a way to suppress sunapi with -Xlint:-sunapi or @SuppressWarnings would provide a path to fixing JDK-8349846.