[mutter] build: Fix srcdir != builddir

[Colin Walters <walters src gnome org>]

commit 115cc870c784f6e0c3cd15a47b7e17e13c902c32
Author: Colin Walters <walters verbum org>
Date:   Sat Aug 17 19:05:50 2013 -0400

    build: Fix srcdir != builddir

 src/Makefile.am |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/Makefile.am b/src/Makefile.am
index 6d40300..e7ada99 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -339,4 +339,4 @@ $(dbus_xrandr_built_sources) : Makefile.am xrandr.xml
                --interface-prefix org.gnome.Mutter                                     \
                --c-namespace MetaDBus                                                  \
                --generate-c-code meta-dbus-xrandr                                      \
-               xrandr.xml
+               $(srcdir)/xrandr.xml