provide temp flag for outside libs to detect multi-backend preview#1243

Titus-von-Koeller merged 2 commits intobitsandbytes-foundation:multi-backend-refactorbitsandbytes-foundation/bitsandbytes:multi-backend-refactorfrom

Titus-von-Koeller:multi-backend-preview-flagTitus-von-Koeller/bitsandbytes:multi-backend-preview-flagCopy head branch name to clipboard