gnu: Add b2sum.

* gnu/packages/crypto.scm (b2sum): New variable.

gnu/packages/crypto.scm

@@ -1,7 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2014 David Thompson <davet@gnu.org>
 ;;; Copyright © 2015, 2017, 2018, 2019 Ricardo Wurmus <rekado@elephly.net>
-;;; Copyright © 2016, 2017, 2018, 2019 Leo Famulari <leo@famulari.name>
+;;; Copyright © 2016, 2017, 2018, 2019, 2021 Leo Famulari <leo@famulari.name>
 ;;; Copyright © 2016 Lukas Gradl <lgradl@openmailbox>
 ;;; Copyright © 2016–2021 Tobias Geerinckx-Rice <me@tobias.gr>
 ;;; Copyright © 2016, 2017 Nikita <nikita@n0.is>
@@ -840,6 +840,41 @@ as the latest standard, SHA-3.  It is an improved version of the SHA-3 finalist
 BLAKE.")
     (license license:public-domain)))
 
+(define-public b2sum
+  ;; Upstream doesn't seem to use a versioned release workflow, so build from
+  ;; a recent commit.
+  (let ((commit "54f4faa4c16ea34bcd59d16e8da46a64b259fc07")
+        (revision "0"))
+    (package
+      (name "b2sum")
+      (version (git-version "20190724" revision commit))
+      (source (origin
+                (method git-fetch)
+                (uri (git-reference
+                       (url "https://github.com/BLAKE2/BLAKE2")
+                       (commit commit)))
+                (file-name (git-file-name name version))
+                (sha256
+                 (base32 "04z631v0vzl52g73v390ask5fnzi5wg83lcjkjhpmmymaz0jn152"))))
+      (build-system gnu-build-system)
+      (arguments
+       `(#:make-flags (list (string-append "CC=" ,(cc-for-target))
+                            (string-append "PREFIX=" (assoc-ref %outputs "out")))
+         #:tests? #f ; No test suite
+         #:phases
+         (modify-phases %standard-phases
+           (add-before 'build 'change-directory
+                       (lambda _
+                         (chdir "b2sum")))
+           (delete 'configure)))) ; No ./configure script
+      (home-page "https://www.blake2.net/")
+      (synopsis "BLAKE2 checksum tool")
+      (description "BLAKE2 is a cryptographic hash function faster than MD5,
+SHA-1, SHA-2, and SHA-3, yet is at least as secure as SHA-3.")
+      ;; You may also choose to redistribute this program as Apache 2.0 or the
+      ;; OpenSSL license. See 'b2sum/b2sum.c' in the source distribution.
+      (license license:cc0))))
+
 (define-public rhash
   (package
     (name "rhash")