Always perform permitted package check when building a library

Previously, the permitted package check was designed to only be run
when building checkbuild. Although, that appears to now be broken.

This change uses a Validation dependency to ensure that the package
check is performed whenever the output file of a java_library is built
as part of the build. The package check runs in parallel with any other
rules that depend on the file.

Bug: 201753898
Test: - change the permitted_packages property in
        frameworks/base/test-mock so that the package check will fail.
      m out/soong/.intermediates/frameworks/base/test-mock/android.test.mock/android_common/package-check.stamp
      - as expected the package check failed.
      m droid
      - as expected the package check did not fail.
      # Made these changes then:
      m droid
      - as expected the package check now failed.
Change-Id: Id38fe280c79e5505ee4555b845c6da2ae6747bc4