Better handle of need_compile_java.

Change-Id: I609a27e2b35b08962243b6516c6c525c0c938d3c
diff --git a/core/static_java_library.mk b/core/static_java_library.mk
index cdb98f0..f95a382 100644
--- a/core/static_java_library.mk
+++ b/core/static_java_library.mk
@@ -126,4 +126,6 @@
 
 endif  # $(all_resources) not empty
 
+# Reset internal variables.
+all_res_assets :=
 LOCAL_IS_STATIC_JAVA_LIBRARY :=