Add SHA256 checksum

We add the SHA256 checksum of the downloaded archive so that Unikraft's
build system is able to do an integrity check of the download.

Signed-off-by: Simon Kuenzer <simon.kuenzer@neclab.eu>
Reviewed-by: Razvan Deaconescu <razvan.deaconescu@cs.pub.ro>
Approved-by: Alexander Jung <a.jung@lancs.ac.uk>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Pull-Request: #4

Makefile.uk

@@ -50,6 +50,8 @@ $(eval $(call addlib_s,libnewlibglue,$(CONFIG_LIBNEWLIBC)))
 LIBNEWLIB_VERSION=2.5.0.20170922
 LIBNEWLIB_URL=http://sourceware.org/pub/newlib/newlib-$(LIBNEWLIB_VERSION).tar.gz
 LIBNEWLIB_PATCHDIR=$(LIBNEWLIBC_BASE)/patches
+LIBNEWLIBC_ORIGIN_SHA256=16ccacbb9155b89a8333da057bfd2952d334795a38dfffcef6a4d83ae12e7275
+
 $(eval $(call fetch,libnewlibc,$(LIBNEWLIB_URL)))
 $(eval $(call patch,libnewlibc,$(LIBNEWLIB_PATCHDIR),newlib-$(LIBNEWLIB_VERSION)))