Reinstate codes to enable RRO on system server

Test: building succeeded and tested with sailfish
Bug: 35742444
Change-Id: I99d0f1d097525d3eb46255d6cf823f6ae2a02385
diff --git a/cmds/idmap/idmap.h b/cmds/idmap/idmap.h
index 5914de9..8d4210b 100644
--- a/cmds/idmap/idmap.h
+++ b/cmds/idmap/idmap.h
@@ -25,6 +25,12 @@
 
 int idmap_create_fd(const char *target_apk_path, const char *overlay_apk_path, int fd);
 
+// Regarding target_package_name: the idmap_scan implementation should
+// be able to extract this from the manifest in target_apk_path,
+// simplifying the external API.
+int idmap_scan(const char *target_package_name, const char *target_apk_path,
+        const char *idmap_dir, const android::Vector<const char *> *overlay_dirs);
+
 int idmap_inspect(const char *idmap_path);
 
 #endif // _IDMAP_H_