[gnome-settings-daemon] build: Fix build problem when gudev is not available

[Ting-Wei Lan <lantw src gnome org>]

commit c5daf94cc073a3c6be7c29c78d3c0475b0b702c4
Author: Ting-Wei Lan <lantw src gnome org>
Date:   Wed Jan 21 19:52:02 2015 +0800

    build: Fix build problem when gudev is not available
    
    https://bugzilla.gnome.org/show_bug.cgi?id=742593

 plugins/common/Makefile.am |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/plugins/common/Makefile.am b/plugins/common/Makefile.am
index daa5193..4400716 100644
--- a/plugins/common/Makefile.am
+++ b/plugins/common/Makefile.am
@@ -28,8 +28,6 @@ libcommon_la_SOURCES = \
        gsd-device-manager.h    \
        gsd-device-manager-x11.c  \
        gsd-device-manager-x11.h  \
-       gsd-device-manager-udev.c \
-       gsd-device-manager-udev.h \
        gsd-device-mapper.c     \
        gsd-device-mapper.h     \
        gsd-keygrab.c           \
@@ -41,6 +39,12 @@ libcommon_la_SOURCES = \
        gsd-shell-helper.c      \
        gsd-shell-helper.h
 
+if HAVE_GUDEV
+libcommon_la_SOURCES += \
+       gsd-device-manager-udev.c \
+       gsd-device-manager-udev.h
+endif
+
 libcommon_la_CPPFLAGS = \
        -I$(top_srcdir)/gnome-settings-daemon   \
        -I$(top_builddir)/gnome-settings-daemon \