Add bzl_library rules for .bzl files without one.
Add bzl_library rules for .bzl files without one.

PiperOrigin-RevId: 325816420
Change-Id: Iaa7191593f13173c80f0a476c0dcda125f8344c4

GoogleCloudPlatform/buildpacks,GoogleCloudPlatform/buildpacks,GoogleCloudPlatform/buildpacks,GoogleCloudPlatform/buildpacks