libostree: disable manpages/documentation generation

--enable-man is set to `auto` as default, which may break builds.

Should fix:

  http://autobuild.buildroot.net/results/43c298afcea20d17bfd9638c8bbee2a912c643be/

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libostree/libostree.mk

@@ -12,7 +12,12 @@ LIBOSTREE_LICENSE = GPL-2.0+
 LIBOSTREE_LICENSE_FILES = COPYING
 LIBOSTREE_DEPENDENCIES = e2fsprogs host-pkgconf libfuse libglib2 libgpgme xz
 
-LIBOSTREE_CONF_OPTS += --with-gpgme-prefix=$(STAGING_DIR)/usr
+LIBOSTREE_CONF_OPTS += \
+	--with-gpgme-prefix=$(STAGING_DIR)/usr \
+	--disable-gtk-doc \
+	--disable-gtk-doc-html \
+	--disable-gtk-doc-pdf \
+	--disable-man
 
 ifeq ($(BR2_PACKAGE_OPENSSL),y)
 LIBOSTREE_CONF_OPTS += --with-openssl