Support LOCAL_SDK_VERSION := core_current

core_current is a pseudo SDK version which is a core Java API subset of
the Android API. It is expected to be mainly used for external Java
projects which are agnostic to Android; such as junit, guava, etc.

A module built with this SDK version can only link to java modules of
the same kind. It can't depend on modules built with LOCAL_SDK_VERSION
:= current or without LOCAL_SDK_VERSION.

Bug: 72206056
Test: m -j
Change-Id: I34a9696393aa6704fd6684a40ea5b05d3fb46b23