[PATCH libmnl] build: do not build documentation automatically

[Pablo Neira Ayuso <pablo@netfilter.org>]

Make it option, after this update it is still possible to build the
documentation on demand via:

 cd doxygen
 make

if ./configure found doxygen. Otherwise, no need to build documentation
when building from source.

Update README to include this information.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 Makefile.am |  2 +-
 README      | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Makefile.am b/Makefile.am
index 94e6935d6138..6ec1a7b98827 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -2,7 +2,7 @@ include $(top_srcdir)/Make_global.am
 
 ACLOCAL_AMFLAGS = -I m4
 
-SUBDIRS = src include examples doxygen
+SUBDIRS = src include examples
 DIST_SUBDIRS = src include examples doxygen
 
 pkgconfigdir = $(libdir)/pkgconfig
diff --git a/README b/README
index 317a2c6ad1d6..c82dedd2266a 100644
--- a/README
+++ b/README
@@ -23,6 +23,16 @@ forced to use them.
 You can find several example files under examples/ that you can compile by
 invoking `make check'.
 
+= Documentation =
+
+If ./configure reports that doxygen has been found, then you can build
+documentation through:
+
+	cd doxygen
+	make
+
+then, open doxygen/html/index.html in your browser.
+
 = Contributing =
 
 Please submit any patches to <netfilter-devel@vger.kernel.org>.
-- 
2.30.2