Add PHONY target for host core.art so that is included in default build
Add PHONY target for host core.art so that is included in default build

Change-Id: I4a2161de73a391b0db953be0e5cd8ec3f79bb9b8

treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst