[seahorse] build: Enable subdir-objects as required

[Rico Tzschichholz <ricotz src gnome org>]

commit e6d601b4ae0a81fc0e1afde689d73567c6cf78ea
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Mon Mar 13 09:46:14 2017 +0100

    build: Enable subdir-objects as required

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index d4ee3dc..0f748e3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -18,7 +18,7 @@ AVAHI_GLIB_REQUIRED=0.6
 # Basic tools
 
 AC_CONFIG_AUX_DIR([build/aux])
-AM_INIT_AUTOMAKE([1.11 tar-ustar foreign -Wno-portability])
+AM_INIT_AUTOMAKE([1.11 tar-ustar foreign -Wno-portability subdir-objects])
 AM_SANITY_CHECK
 AC_CONFIG_HEADERS([build/config.h])
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])