gnu: libgc: Add version 8.0.4.

* gnu/packages/bdw-gc.scm (libgc-8.0): New variable.

gnu/packages/bdw-gc.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2016, 2017, 2020 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2016, 2018 Leo Famulari <leo@famulari.name>
 ;;; Copyright © 2017 Rene Saavedra <rennes@openmailbox.org>
@@ -91,6 +91,18 @@ C or C++ programs, though that is not its primary goal.")
 
    (license (x11-style (string-append home-page "license.txt")))))
 
+(define-public libgc-8.0
+  (package/inherit
+   libgc
+   (version "8.0.4")
+   (source (origin
+             (method url-fetch)
+             (uri (string-append "https://github.com/ivmai/bdwgc/releases"
+                                 "/download/v" version "/gc-" version ".tar.gz"))
+             (sha256
+              (base32
+               "1798rp3mcfkgs38ynkbg2p47bq59pisrc6mn0l20pb5iczf0ssj3"))))))
+
 (define-public libgc/back-pointers
   (package
     (inherit libgc)