[libxslt] Don't fail build the man page if xsltproc is not present

[Daniel Veillard <veillard src gnome org>]

commit 5b879369aff636b1591f9e5ccdd2150d3f7df7fb
Author: Daniel Veillard <veillard redhat com>
Date:   Mon Jun 29 20:31:37 2015 +0800

    Don't fail build the man page if xsltproc is not present

 doc/Makefile.am |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/doc/Makefile.am b/doc/Makefile.am
index 566945d..48ad61c 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -240,7 +240,9 @@ libxslt-api.xml libxslt-refs.xml EXSLT/libexslt-api.xml \
        ($(XSLTPROC) -o ../libxslt/libxslt.syms $(srcdir)/syms.xsl $(srcdir)/symbols.xml)
 
 xsltproc.1: $(srcdir)/xsltproc.xml
-       - $(XSLTPROC) --nonet $(srcdir)/xsltproc.xml
+       -@(if [ -x $(XSLTPROC) ] ; then \
+          echo "Rebuilding the man pages from the xml" ; \
+          $(XSLTPROC) --nonet $(srcdir)/xsltproc.xml );
 
 # Note that in the following, xmllint output is piped to xsltproc
 search.php: $(srcdir)/api.xsl $(srcdir)/site.xsl $(srcdir)/search.templ \