Support unique_host_soname to add -host for shared libs

In order to distinguish our host libraries from system installed
libraries, support a flag to automatically append -host to host shared
libraries names. Previously, we were implementing this with different modules,
but with Soong, we'd really like to share the module definitions.

This properly exports the module to make, so that
LOCAL_SHARED_LIBRARIES := libcrypto still works, but the final installed
name is libcrypto-host.so.

Change-Id: I63389469fe1b38078b8bbf4c0fd92e54ef90ae1a

cc/androidmk.go

@@ -99,6 +99,7 @@ func (library *libraryLinker) AndroidMk(ctx AndroidMkContext, ret *android.Andro
 		}
 
 		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+outputFile.Ext())
+		fmt.Fprintln(w, "LOCAL_BUILT_MODULE_STEM := $(LOCAL_MODULE)$(LOCAL_MODULE_SUFFIX)")
 
 		fmt.Fprintln(w, "LOCAL_SYSTEM_SHARED_LIBRARIES :=")