Compile against "core_current" not SDK stubs

This library is used from libcore tests and so we
want it to only depend on public SDK APIs from
core libraries. It's not used elsewhere so we
can safely switch it.

Bug: 113148576
Test: build
Change-Id: Id190ec21a658532184e273a5cf3536208ee30174
diff --git a/Android.bp b/Android.bp
index 3fbb48b..16f50ac 100644
--- a/Android.bp
+++ b/Android.bp
@@ -21,7 +21,6 @@
         "shared/src/main/java/**/*.java",
         "applier/src/main/java/**/*.java",
     ],
-    // archive-patcher should be compatible with all versions of Android
-    sdk_version: "4",
+    sdk_version: "core_current",
     java_version: "1.6",
 }