[libxmlplusplus] docs/manual: Fix builddir != sourcedir builds

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 48dcb480f86895956ee0d14a0a556514c72e876e
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Thu Jan 3 17:18:15 2019 +0100

    docs/manual: Fix builddir != sourcedir builds

 docs/Makefile.am | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/docs/Makefile.am b/docs/Makefile.am
index 8011c32..8dfc7b2 100644
--- a/docs/Makefile.am
+++ b/docs/Makefile.am
@@ -22,7 +22,8 @@ doc_input = $(addprefix $(top_srcdir)/libxml++/,$(h_sources_public))
 include $(top_srcdir)/build/doc-reference.am
 
 manual/libxml++.xml: ${top_srcdir}/docs/manual/libxml++_without_code.xml 
${top_srcdir}/docs/manual/insert_example_code.pl
-       $(AM_V_GEN)$(PERL) -- ${top_srcdir}/docs/manual/insert_example_code.pl ../examples $< >$@
+       $(AM_V_at)$(MKDIR_P) manual
+       $(AM_V_GEN)$(PERL) -- ${top_srcdir}/docs/manual/insert_example_code.pl ${top_srcdir}/examples $< >$@
 
 manualdir = $(docdir)/manual
 manual_htmldir = $(manualdir)/html