[lightsoff] Fix appdata installation

[Kalev Lember <klember src gnome org>]

commit e402cf6bdd165fa94999f748eb90c766600935b2
Author: Kalev Lember <klember redhat com>
Date:   Mon Feb 5 12:51:46 2018 +0100

    Fix appdata installation
    
    Add back @APPSTREAM_XML_RULES@ to Makefile.am to make sure the appdata
    file gets installed. This regressed in commit f7d3515 that accidentally
    dropped the rules.

 data/Makefile.am |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/data/Makefile.am b/data/Makefile.am
index 56e225b..d547043 100644
--- a/data/Makefile.am
+++ b/data/Makefile.am
@@ -21,6 +21,7 @@ $(desktop_DATA): $(desktop_in_files)
 
 appstream_in_files = lightsoff.appdata.xml.in
 appstream_XML = $(appstream_in_files:.xml.in=.xml)
+@APPSTREAM_XML_RULES@
 $(appstream_XML): $(appstream_in_files)
        $(AM_V_GEN)$(MSGFMT) --xml --template $< -d $(top_srcdir)/po -o $@