Allow soong java libraries to include exported resources and proguard flags

Test: m checkbuild
Change-Id: Ia02f816084d0eb1c0e0f20e1ecd57aaf3778874c
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index baa2344..3bec869 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -235,6 +235,7 @@
 LOCAL_SHARED_LIBRARIES:=
 LOCAL_SOONG_CLASSES_JAR :=
 LOCAL_SOONG_DEX_JAR :=
+LOCAL_SOONG_EXPORT_PROGUARD_FLAGS :=
 LOCAL_SOONG_HEADER_JAR :=
 LOCAL_SOONG_JACOCO_REPORT_CLASSES_JAR :=
 LOCAL_SOONG_PROGUARD_DICT :=