Add ANDROID_LINK_SHARED_ICU4C flag

The allows the libtextclassifier to link libicuuc
until libtextclassifier is migrated to use java icu.

libicuuc and libicui18n are moved into APEX, but
they have no stable ABI due to the version suffix.

Use libandroidicu which provides stable symbol.
See http://go/apex-stable-icu4c-interface for the design.

Test: m checkbuild
Bug: 117094880
Merged-In: Ib4e0efa8d0da0162d6d57bbf58a0b2836c784f75
Change-Id: Ib4e0efa8d0da0162d6d57bbf58a0b2836c784f75