[rygel] build: Remove useless use of cat

[Jens Georg <jensgeorg src gnome org>]

commit d9e3d3eb0357b9bdd8bd6e692d94eddfd98acd2b
Author: Jens Georg <mail jensge org>
Date:   Mon May 1 10:36:37 2017 +0200

    build: Remove useless use of cat

 data/xml/Makefile.am |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/data/xml/Makefile.am b/data/xml/Makefile.am
index d68e460..3cd94a6 100644
--- a/data/xml/Makefile.am
+++ b/data/xml/Makefile.am
@@ -16,7 +16,7 @@ xml_DATA = $(xml_in_files:.xml.in=.xml)
 
 # Strip newlines and leading spaces from XML files as not all devices like them
 %.xml: %.xml.in
-       @cat < $< | sed -re "s,^ +,,g" | tr -d "\n" > $@
+       @$(SED) -re "s,^ +,,g" < $< | tr -d "\n" > $@
 
 xmldir = $(datadir)/rygel/xml