Allow the unsupportedappusage-annotation to be used for device variants

Some modules, e.g. libphonenumber-platform, depend on core platform API
solely for accessing the dalvik.annotation.compat.UnsupportedAppUsage
annotation. Building device variants of unsupportedappusage-annotation
will allow those modules to switch to core_current.

Bug: 134379140
Test: m droid
Change-Id: I1634b8ffd2a28c2663defd2a4a4e40d78b174d91
diff --git a/Android.bp b/Android.bp
index 6d16f6d..7dcafb6 100644
--- a/Android.bp
+++ b/Android.bp
@@ -758,15 +758,22 @@
     plugins: ["unsupportedappusage-annotation-processor"],
 }
 
-// A host library including just UnsupportedAppUsage.java so that the annotation
-// processor can also use this annotation.
-java_library_host {
+// A library including just UnsupportedAppUsage.java classes.
+//
+// Provided for target so that libraries can use it without depending on
+// the whole of framework or the core platform API.
+//
+// Built for host so that the annotation processor can also use this annotation.
+java_library {
     name: "unsupportedappusage-annotation",
+    host_supported: true,
     srcs: [
         "core/java/android/annotation/IntDef.java",
         "core/java/android/annotation/UnsupportedAppUsage.java",
         ":unsupportedappusage_annotation_files",
     ],
+
+    sdk_version: "core_current",
 }
 
 // A temporary build target that is conditionally included on the bootclasspath if