Update checkapi error message to provide more guidance

With from-text stub feature, checkapi is also used for checking the
sanity of the stubs. Therefore, this change adds more explanatory
message about how the user can rebuild the target when their build
failed with stub validation after local API change.

Test: m nothing
Bug: 309027703
Change-Id: If7c9c287266f3da82edde663619b9f08ee05530d