Set compile_dex for sdk prebuilts.

Bug: 160455085
Test: m
Change-Id: Ie3c000192556cda0019fb99b2568ea4920a73bed
diff --git a/Android.bp b/Android.bp
index d3c9831..0085093 100644
--- a/Android.bp
+++ b/Android.bp
@@ -113,4 +113,5 @@
         "current",
     ],
     imports_sdk_version: "none",
+    imports_compile_dex: true,
 }