[mutter] Makefile: Use $(NULL) trick

[Jasper St. Pierre <jstpierre src gnome org>]

commit f8a4d450a50c7db3af485656500c5087da35b10c
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Tue Nov 4 19:06:55 2014 -0800

    Makefile: Use $(NULL) trick
    
    This helps make the Makefile look nicer and prevent merge conflicts.

 src/Makefile.am |   45 +++++++++++++++++++++++++++------------------
 1 files changed, 27 insertions(+), 18 deletions(-)
---
diff --git a/src/Makefile.am b/src/Makefile.am
index 0c601d2..353b66f 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -6,6 +6,7 @@ lib_LTLIBRARIES = libmutter.la
 SUBDIRS=compositor/plugins
 
 EXTRA_DIST =
+NULL =
 
 AM_CPPFLAGS = \
        -DCLUTTER_ENABLE_COMPOSITOR_API                                 \
@@ -31,26 +32,30 @@ AM_CPPFLAGS = \
        -DMUTTER_PKGLIBDIR=\"$(pkglibdir)\"                             \
        -DMUTTER_PLUGIN_DIR=\"$(MUTTER_PLUGIN_DIR)\"                    \
        -DGETTEXT_PACKAGE=\"$(GETTEXT_PACKAGE)\"                        \
-       -DXWAYLAND_PATH=\"$(XWAYLAND_PATH)\"
+       -DXWAYLAND_PATH=\"$(XWAYLAND_PATH)\"                            \
+       $(NULL)
 
 mutter_built_sources = \
        $(dbus_idle_built_sources)              \
        $(dbus_display_config_built_sources)    \
        $(dbus_login1_built_sources)            \
        mutter-enum-types.h                     \
-       mutter-enum-types.c
+       mutter-enum-types.c                     \
+       $(NULL)
 
 if HAVE_WAYLAND
 mutter_built_sources += \
        gtk-shell-protocol.c                    \
        gtk-shell-server-protocol.h             \
        xdg-shell-protocol.c                    \
-       xdg-shell-server-protocol.h
+       xdg-shell-server-protocol.h             \
+       $(NULL)
 endif
 
-wayland_protocols = \
+wayland_protocols =                            \
        wayland/protocol/gtk-shell.xml          \
-       wayland/protocol/xdg-shell.xml
+       wayland/protocol/xdg-shell.xml          \
+       $(NULL)
 
 libmutter_la_SOURCES =                         \
        backends/meta-backend.c                 \
@@ -220,7 +225,8 @@ libmutter_la_SOURCES =                              \
        x11/window-x11-private.h                \
        x11/xprops.c                            \
        x11/xprops.h                            \
-       x11/mutter-Xatomtype.h
+       x11/mutter-Xatomtype.h                  \
+       $(NULL)
 
 if HAVE_WAYLAND
 libmutter_la_SOURCES +=                                \
@@ -253,7 +259,8 @@ libmutter_la_SOURCES +=                             \
        wayland/meta-wayland-outputs.c          \
        wayland/meta-wayland-outputs.h          \
        wayland/window-wayland.c                \
-       wayland/window-wayland.h
+       wayland/window-wayland.h                \
+       $(NULL)
 endif
 
 if HAVE_NATIVE_BACKEND
@@ -269,11 +276,11 @@ libmutter_la_SOURCES +=                                   \
        backends/native/meta-launcher.c                 \
        backends/native/meta-launcher.h                 \
        backends/native/dbus-utils.c                    \
-       backends/native/dbus-utils.h
+       backends/native/dbus-utils.h                    \
+       $(NULL)
 endif
 
-nodist_libmutter_la_SOURCES =                  \
-       $(mutter_built_sources)
+nodist_libmutter_la_SOURCES = $(mutter_built_sources)
 
 libmutter_la_LDFLAGS = -no-undefined
 libmutter_la_LIBADD  = $(MUTTER_LIBS) $(MUTTER_NATIVE_BACKEND_LIBS)
@@ -308,7 +315,8 @@ libmutterinclude_headers =                  \
        meta/types.h                            \
        meta/util.h                             \
        meta/window.h                           \
-       meta/workspace.h
+       meta/workspace.h                        \
+       $(NULL)
 
 libmutterinclude_built_headers =               \
        meta/meta-version.h
@@ -389,14 +397,15 @@ DISTCLEANFILES =                          \
 pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = libmutter.pc
 
-EXTRA_DIST +=                          \
-       $(wayland_protocols)            \
-       libmutter.pc.in \
-       mutter-enum-types.h.in \
-       mutter-enum-types.c.in \
-       org.freedesktop.login1.xml      \
+EXTRA_DIST +=                                  \
+       $(wayland_protocols)                    \
+       libmutter.pc.in                         \
+       mutter-enum-types.h.in                  \
+       mutter-enum-types.c.in                  \
+       org.freedesktop.login1.xml              \
        org.gnome.Mutter.DisplayConfig.xml      \
-       org.gnome.Mutter.IdleMonitor.xml
+       org.gnome.Mutter.IdleMonitor.xml        \
+       $(NULL)
 
 BUILT_SOURCES =                                        \
        $(mutter_built_sources)                 \