Update to bashbrew 0.1.7

[tianon]

Notably, this adds support for Builder: oci-import:

• add (experimental) Builder: oci-import support (Add "Builder: oci-import" support bashbrew#61)
  • see Add "Builder: oci-import" support bashbrew#61 (comment) for an example of the intended usage
    Directory: pointing to an "OCI Image Layout" and File: pointing to either a single-entry "OCI Image Index" or a single raw "OCI Content Descriptor" (in either case, pointing to a single per-architecture "OCI Image Manifest" object within the blobs/ directory)

[tianon]

See also docker-library/bashbrew#51: the most important call-out here is that this is intended for base images where we're effectively swapping a super-basic three-line Dockerfile (FROM scratch + ADD rootfs.xxx / + CMD ["..."]) that creates rootfs metadata as a side effect for an explicit JSON file that contains the pre-calculated metadata such that an architecture image's individual content-addressable digest is preserved all the way through our pipeline.

This is not intended for non-base images, and new images / image updates which attempt to do so will likely be rejected during review.