Fix mis-optimization of BUILDPLAN with MI
Fix mis-optimization of BUILDPLAN with MI

We cannot just take the BUILDPLAN from the next thing along in the MRO
if it's not the single parent of this class. Fixes #2782.

tony-o/rakudo,softmoth/rakudo,tony-o/rakudo,tony-o/rakudo,rakudo/rakudo,softmoth/rakudo,salortiz/rakudo,labster/rakudo,MasterDuke17/rakudo,tony-o/rakudo,nbrown/rakudo,rakudo/rakudo,rakudo/rakudo,softmoth/rakudo,nbrown/rakudo,tbrowder/rakudo,tbrowder/rakudo,tbrowder/rakudo,salortiz/rakudo,salortiz/rakudo,nbrown/rakudo,salortiz/rakudo,MasterDuke17/rakudo,nbrown/rakudo,salortiz/rakudo,nbrown/rakudo,tbrowder/rakudo,softmoth/rakudo,rakudo/rakudo,MasterDuke17/rakudo,labster/rakudo,softmoth/rakudo,MasterDuke17/rakudo,rakudo/rakudo,tony-o/rakudo,tbrowder/rakudo,labster/rakudo,rakudo/rakudo,labster/rakudo,MasterDuke17/rakudo,labster/rakudo,MasterDuke17/rakudo,nbrown/rakudo,tony-o/rakudo,tbrowder/rakudo,salortiz/rakudo,labster/rakudo