Migrating Our iOS Build System from Buck to Bazel

Airbnb recently migrated its iOS build system from Buck to Bazel to provide a cohesive and efficient build experience across all platforms. The migration process involved reusing the Buck configurations in Bazel to avoid disruptions during the transition period. The build configuration files were modified to work with both Buck and Bazel, with a layer introduced to provide the same interface for each application. This allowed for minimal changes to the build files themselves. The migration was done in three phases, with Buck-generated Xcode workspaces used for local development. The successful migration of the iOS build system is part of Airbnb's larger effort to migrate to Bazel for other platforms as well.