Check for sphinx-build during configure

configure.ac

@@ -90,6 +90,10 @@ AC_PATH_PROG([ASCIIDOC], [asciidoc])
 AC_SUBST([ASCIIDOC])
 AM_CONDITIONAL([HAVE_ASCIIDOC], [ test "x$ASCIIDOC" != "x" ])
 
+AC_PATH_PROGS([SPHINXBUILD], [sphinx-build])
+AC_SUBST([SPHINXBUILD])
+AM_CONDITIONAL([HAVE_SPHINXBUILD], [ test "x$SPHINXBUILD" != "x" ])
+
 AC_PATH_PROGS([RST2HTML], [rst2html.py rst2html])
 AC_SUBST([RST2HTML])
 AM_CONDITIONAL([HAVE_RST2HTML], [ test "x$RST2HTML" != "x" ])

doc/Makefile.am

@@ -1,4 +1,6 @@
+if HAVE_SPHINXBUILD
 SUBDIRS = manual-src
+endif #SPHINXBUILD
 
 doc_xmlrpcdir = $(docdir)/xmlrpc
 dist_doc_xmlrpc_DATA = xmlrpc/aria2mon \