libxml2 now depends on libandroidicu.
Add the same dependency into the VTS.
TODO: b/121468463 to remove ICU from VtsHalAudio
Bug: 117094880
Test: m checkbuild
Merged-In: I105e7ad1517ecf8780adfb730650e1ad82f65857
Change-Id: I105e7ad1517ecf8780adfb730650e1ad82f65857