When a custom buildpack is provided for image building, the contents
of the buildpack directory, tgz file, or image are copied as tar
entries to a new layer in the ephemeral builder image. Prior to this
commit, only file entries from the buildpack source were copied as
builder layer tar entries; intermediate directory entries from the
source were not copied. This results in directories being created in
the builder container using default permissions. This worked on most
Linux-like OSs where the default permissions allow others-read
access. On some OSs like Arch Linux where the default directory
permissions do not allow others-read, this prevented the lifecycle
processes from reading the buildpack files.

This commit explicitly creates all intermediate directory tar entries
in the builder image layer to ensure that the buildpack directories
and files can be read by the lifecycle processes.

Fixes gh-26658