[gobject-introspection] autotools: fix missing version api in gtk-doc for non-srcdir builds

[Christoph Reiter <creiter src gnome org>]

commit 03385b905a4ebaef26b0e5b1d6ef3bc9a075b69c
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Tue Jan 1 01:48:56 2019 +0100

    autotools: fix missing version api in gtk-doc for non-srcdir builds
    
    Properly pass the build dir paths to gtk-doc so it can find things in giversion.h
    
    This fixes the version section being empty when building the docs with non-srcdir autotools.

 docs/reference/Makefile.am | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/docs/reference/Makefile.am b/docs/reference/Makefile.am
index ee953bb7..2354f915 100644
--- a/docs/reference/Makefile.am
+++ b/docs/reference/Makefile.am
@@ -13,7 +13,7 @@ DOC_MAIN_SGML_FILE=gi-docs.xml
 # gtk-doc will search all .c and .h files beneath these paths
 # for inline comments documenting functions and macros.
 # e.g. DOC_SOURCE_DIR=$(top_srcdir)/gtk $(top_srcdir)/gdk
-DOC_SOURCE_DIR=$(top_srcdir)/girepository
+DOC_SOURCE_DIR=$(top_srcdir)/girepository $(top_builddir)/girepository
 
 # Extra options to pass to gtkdoc-scangobj. Not normally needed.
 SCANGOBJ_OPTIONS=
@@ -40,7 +40,7 @@ FIXXREF_OPTIONS=
 # Used for dependencies. The docs will be rebuilt if any of these change.
 # e.g. HFILE_GLOB=$(top_srcdir)/gtk/*.h
 # e.g. CFILE_GLOB=$(top_srcdir)/gtk/*.c
-HFILE_GLOB=$(top_srcdir)/girepository/*.h
+HFILE_GLOB=$(top_srcdir)/girepository/*.h $(top_builddir)/girepository/*.h
 CFILE_GLOB=$(top_srcdir)/girepository/*.c
 
 # Extra header to include when scanning, which are not under DOC_SOURCE_DIR