Fix #1804: Do binary compat checks only for published artifacts.
Fix #1804: Do binary compat checks only for published artifacts.

It is irrelevant, and wrong, to check binary compatibility checks
with Scala versions that are not actually used to *publish* the
artifacts. Doing them caused some checks to fail when testing
with earlier versions of the Scala compiler, because more recent
versions produce less private boilerplate members.

CapeSepias/scala-js,japgolly/scala-js,sjrd/scala-js,jasonchaffee/scala-js,Vp3n/scala-js,andreaTP/scala-js,CapeSepias/scala-js,jmnarloch/scala-js,japgolly/scala-js,scala-js/scala-js,xuwei-k/scala-js,gzm0/scala-js,nicolasstucki/scala-js,renyaoxiang/scala-js,sjrd/scala-js,mdedetrich/scala-js,jasonchaffee/scala-js,xuwei-k/scala-js,spaced/scala-js,jmnarloch/scala-js,SebsLittleHelpers/scala-js,japgolly/scala-js,mdedetrich/scala-js,mdedetrich/scala-js,scala-js/scala-js,lrytz/scala-js,xuwei-k/scala-js,SebsLittleHelpers/scala-js,spaced/scala-js,gzm0/scala-js,sjrd/scala-js,andreaTP/scala-js,renyaoxiang/scala-js,doron123/scala-js,ummels/scala-js,Vp3n/scala-js,ummels/scala-js,doron123/scala-js,CapeSepias/scala-js,jmnarloch/scala-js,andreaTP/scala-js,scala-js/scala-js,renyaoxiang/scala-js,ummels/scala-js,spaced/scala-js,lrytz/scala-js,Vp3n/scala-js,doron123/scala-js,jasonchaffee/scala-js,nicolasstucki/scala-js