There isn't an OOTB way to do this, although it may be possible to deconfigure the Quartz job that kicks it off then write some code that manually kicks off the same logic instead (I'd likely implement this as a Web Script, since they can be readily scripted from the command line etc.). The bit I'm not sure about is the API you'd call from that code - I'm assuming there's a clean "backup Lucene indexes" API that the Quartz job calls, but I haven't dug into that code myself.
Another option is to run your backup prior to the Lucene index backup. While this will result in slightly more stale Lucene indexes in the backup set, that's no big deal since Alfresco will incrementally rebuild the indexes if a backup is restored, and unless there are a lot of changes to the content each and every day this shouldn't be too expensive.
Cheers,
Peter
