release: split out sha256 upload (#2063)

For the 1.2.1 release we didn't upload the sha256 files. I've added
an echo, but some testing suggests that the files are created, so the
problem lays somewhere else.

Add a new upload section that sets the content type correctly and POST
the files as text/plain.
Signed-off-by: Miek Gieben <miek@miek.nl>

Makefile.release

@@ -97,13 +97,20 @@ github-push:
 	@echo Releasing: $(VERSION)
 	@$(eval RELEASE:=$(shell curl -s -d '{"tag_name": "v$(VERSION)", "name": "v$(VERSION)"}' "https://api.github.com/repos/$(GITHUB)/$(NAME)/releases?access_token=${GITHUB_ACCESS_TOKEN}" | grep -m 1 '"id"' | tr -cd '[[:digit:]]'))
 	@echo ReleaseID: $(RELEASE)
-	@for asset in `ls -A release`; do \
+	@for asset in `ls -A release/*tgz`; do \
 	    echo $$asset; \
 	    curl -o /dev/null -X POST \
 	      -H "Content-Type: application/gzip" \
 	      --data-binary "@release/$$asset" \
 	      "https://uploads.github.com/repos/$(GITHUB)/$(NAME)/releases/$(RELEASE)/assets?name=$${asset}&access_token=${GITHUB_ACCESS_TOKEN}" ; \
 	done
+	@for asset in `ls -A release/*sha256`; do \
+	    echo $$asset; \
+	    curl -o /dev/null -X POST \
+	      -H "Content-Type: text/plain" \
+	      --data-binary "@release/$$asset" \
+	      "https://uploads.github.com/repos/$(GITHUB)/$(NAME)/releases/$(RELEASE)/assets?name=$${asset}&access_token=${GITHUB_ACCESS_TOKEN}" ; \
+	done
 
 .PHONY: docker-build
 docker-build: tar