[mutter] build: Fix gtk-doc build failure when native backend is disabled

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

commit 638087fe78aa6c50e1c93d2747301eb44e078a8d
Author: Ting-Wei Lan <lantw src gnome org>
Date:   Wed Sep 17 13:31:26 2014 +0800

    build: Fix gtk-doc build failure when native backend is disabled
    
    https://bugzilla.gnome.org/show_bug.cgi?id=731521

 doc/reference/Makefile.am |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/doc/reference/Makefile.am b/doc/reference/Makefile.am
index bf3a588..b1587b0 100644
--- a/doc/reference/Makefile.am
+++ b/doc/reference/Makefile.am
@@ -111,6 +111,15 @@ IGNORE_HFILES= \
        xprops.h \
        $(NULL)
 
+if !HAVE_NATIVE_BACKEND
+IGNORE_HFILES+= \
+       meta-backend-native.h \
+       meta-cursor-renderer-native.h \
+       meta-idle-monitor-native.h \
+       meta-monitor-manager-kms.h \
+       $(NULL)
+endif
+
 if !HAVE_WAYLAND
 IGNORE_HFILES += \
        meta-surface-actor-wayland.h    \