Allow to build Java module from mere static Java libraries.

With this change, we can easily turn a static Java library to a shared
Java library.

Change-Id: I9915992cd19879846511d6272483d7a0a934e7eb
diff --git a/core/base_rules.mk b/core/base_rules.mk
index 242b53d..668271e 100644
--- a/core/base_rules.mk
+++ b/core/base_rules.mk
@@ -381,7 +381,7 @@
 
 ## PRIVATE java vars ######################################
 
-ifneq ($(strip $(all_java_sources)$(all_res_assets)),)
+ifneq ($(strip $(all_java_sources)$(all_res_assets))$(LOCAL_STATIC_JAVA_LIBRARIES),)
 
 full_static_java_libs := \
     $(foreach lib,$(LOCAL_STATIC_JAVA_LIBRARIES), \