Fix Hex package downloads on FreeBSD

Error has been detected during the nightly packages build.

core/deps.mk

@@ -503,7 +503,7 @@ define dep_fetch_hex
 	mkdir -p $(ERLANG_MK_TMP)/hex $(DEPS_DIR)/$1; \
 	$(call core_http_get,$(ERLANG_MK_TMP)/hex/$1.tar,\
 		https://s3.amazonaws.com/s3.hex.pm/tarballs/$1-$(strip $(word 2,$(dep_$1))).tar); \
-	tar -xOf $(ERLANG_MK_TMP)/hex/$1.tar contents.tar.gz | tar -C $(DEPS_DIR)/$1 -xz;
+	tar -xOf $(ERLANG_MK_TMP)/hex/$1.tar contents.tar.gz | tar -C $(DEPS_DIR)/$1 -xzf -;
 endef
 
 define dep_fetch_fail