Always generate -host phony target for host modules

HostCross variants will create an additional -host-cross phony. This
matches the implementation in build/make/core/base_rules.mk

With this CL, phony targets like `adb-host` will be created.

Test: verified that adb-host phony exists in soong only build
Change-Id: I9daf890bbde7e27c49a3f9f8ba78238991a8cf43