[clutter] build: Add top_builddir to the API reference sources

[Emmanuele Bassi <ebassi src gnome org>]

commit 73e6f4e69df1b464c40e4652ed3cffccb003e7bb
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Tue Mar 3 15:54:36 2015 +0000

    build: Add top_builddir to the API reference sources
    
    Otherwise gtk-doc won't be able to find some generated files.

 doc/reference/clutter/Makefile.am |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/doc/reference/clutter/Makefile.am b/doc/reference/clutter/Makefile.am
index 8a28069..623ec3b 100644
--- a/doc/reference/clutter/Makefile.am
+++ b/doc/reference/clutter/Makefile.am
@@ -5,7 +5,7 @@ DOC_MAIN_SGML_FILE = $(DOC_MODULE)-docs.xml
 # gtk-doc will search all .c & .h files beneath here for inline comments
 # documenting the functions and macros.
 # e.g. DOC_SOURCE_DIR=../../../gtk
-DOC_SOURCE_DIR = ../../../clutter
+DOC_SOURCE_DIR = $(top_srcdir)/clutter $(top_builddir)/clutter
 
 # Extra options to pass to gtkdoc-scangobj. Not normally needed.
 SCANGOBJ_OPTIONS = --type-init-func="clutter_base_init()"