Build junit with core_current

Using core_current ensures that the module is not using any Android APIs
(e.g. APIs under android.* packages), but only core Java APIs.

Bug: 72206056
Test: m -j junit
Change-Id: I7de7caf4324c088d330cadb69e03d67b8dcdc84e
diff --git a/Android.bp b/Android.bp
index 7d92bc7..b0e24e5 100644
--- a/Android.bp
+++ b/Android.bp
@@ -19,7 +19,7 @@
     host_supported: true,
     hostdex: true,
     srcs: ["src/main/java/**/*.java"],
-    sdk_version: "25",
+    sdk_version: "core_current",
     static_libs: ["hamcrest"],
 }