[gnome-software] trivial: Fix make distcheck after recent commit

[Richard Hughes <rhughes src gnome org>]

commit a34adaf2915213494e590ccfc92f128b97138bec
Author: Richard Hughes <richard hughsie com>
Date:   Fri Jan 29 20:49:17 2016 +0000

    trivial: Fix make distcheck after recent commit

 src/Makefile.am |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/Makefile.am b/src/Makefile.am
index 0013150..b4a0792 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -261,6 +261,7 @@ gs_self_test_SOURCES =                                              \
        gs-app.c                                                \
        gs-category.c                                           \
        gs-markdown.c                                           \
+       gs-os-release.c                                         \
        gs-plugin-loader-sync.c                                 \
        gs-plugin-loader.c                                      \
        gs-plugin.c                                             \