contrib: update nettle

Change-Id: I5faea9221c6c6c60e75e5b9cc31559a900892a23

contrib/src/nettle/SHA512SUMS

-2471af875e51327af61af8bda53cd9c3adc27b6e32592a4b5b10b3ec60999ebf771ab9c54c747b0bade4b3b5a717e77fdbdb53699dd9e8a9ed4eee07f46aed51  nettle-3.6.tar.gz
+559d2afdbfb1ab0de2231e04b1ab15c11e1c38dc5a859f2f9f64124d6370a310319977d6ba7628ae2e1234e5821a7d7182bfdfc7f7475be9276cd69481c3447e  nettle-91df68136ad1562cf9217599254706d8cfa970ea.tar.gz

contrib/src/nettle/rules.mak

 # Nettle
 
-NETTLE_VERSION := 3.6
-NETTLE_URL := $(GNU)/nettle/nettle-$(NETTLE_VERSION).tar.gz
-
+NETTLE_VERSION := 91df68136ad1562cf9217599254706d8cfa970ea
+NETTLE_URL := https://git.lysator.liu.se/aberaud/nettle/-/archive/$(NETTLE_VERSION)/nettle-$(NETTLE_VERSION).tar.gz
 PKGS += nettle
 
 ifeq ($(call need_pkg,"nettle >= 3.4.1"),)
@@ -24,10 +23,8 @@ DEPS_nettle = gmp
 .nettle: nettle
 ifdef HAVE_IOS
 	cd $< && sed -i.orig s/-ggdb3//g configure.ac
+endif
 	cd $< && autoreconf
-	cd $< && $(HOSTVARS) CFLAGS="$(CFLAGS) -O3" ./configure $(HOSTCONF)
-else
 	cd $< && $(HOSTVARS) ./configure --disable-documentation $(HOSTCONF)
-endif
 	cd $< && $(MAKE) install
 	touch $@