nettle: don't build documentation

Change-Id: Ib2526273a70c21734fe3e5b12297b1dfdfdc0207
Reviewed-by: Sebastien Blin <sebastien.blin@savoirfairelinux.com>

contrib/src/nettle/rules.mak

@@ -27,7 +27,7 @@ ifdef HAVE_IOS
 	cd $< && autoreconf
 	cd $< && $(HOSTVARS) CFLAGS="$(CFLAGS) -O3" ./configure $(HOSTCONF)
 else
-	cd $< && $(HOSTVARS) ./configure $(HOSTCONF)
+	cd $< && $(HOSTVARS) ./configure --disable-documentation $(HOSTCONF)
 endif
 	cd $< && $(MAKE) install
 	touch $@