gnu: racket: Update to 7.6.

* gnu/packages/scheme.scm (racket): Update to 7.6.
[home-page]: Use HTTPS.
* gnu/packages/patches/racket-store-checksum-override.patch: Adjust for 7.6.

gnu/packages/patches/racket-store-checksum-override.patch

@@ -11,26 +11,15 @@ See <https://debbugs.gnu.org/30680> for details.
 ---
 --- a/collects/compiler/private/cm-minimal.rkt
 +++ b/collects/compiler/private/cm-minimal.rkt
-@@ -7,6 +7,7 @@
+@@ -6,6 +6,7 @@
           racket/list
           racket/path
           racket/promise
 +         racket/string
           file/sha1
-          setup/collects
           setup/cross-system
-@@ -940,6 +941,10 @@
+          compiler/compilation-path
-       #f
+@@ -268,7 +269,8 @@
-       (list src-hash recorded-hash)))
- 
-+(define (store-reference? path)
-+  (let ([store-prefix (or (getenv "NIX_STORE") "/gnu/store")])
-+    (string-prefix? (path->string path) store-prefix)))
-+
- (define (rkt->ss p)
-   (if (path-has-extension? p #".rkt")
-       (path-replace-extension p #".ss")
-@@ -1015,6 +1020,7 @@
                 (trace-printf "newer src... ~a > ~a" path-time path-zo-time)
                 (maybe-compile-zo deps path->mode roots path orig-path read-src-syntax up-to-date collection-cache new-seen
                                   #:trying-sha1? sha1-only?)]
@@ -40,3 +29,14 @@ See <https://debbugs.gnu.org/30680> for details.
                 => (lambda (difference)
                      (trace-printf "different src hash ~a for ~a..." difference path)
                      (maybe-compile-zo deps path->mode roots path orig-path read-src-syntax up-to-date collection-cache new-seen
+@@ -1012,5 +1014,9 @@
+       #f
+       (list src-hash recorded-hash)))
+
++(define (store-reference? path)
++  (let ([store-prefix (or (getenv "NIX_STORE") "/gnu/store")])
++    (string-prefix? (path->string path) store-prefix)))
++
+ ;; Make sure `recompile-from` is machine-independent so that
+ ;; recompilation makes sense.
+ ;; The compilation lock must is held for the source of `recompile-from`.

gnu/packages/scheme.scm

@@ -11,6 +11,7 @@
 ;;; Copyright © 2017, 2018, 2019, 2020 Tobias Geerinckx-Rice <me@tobias.gr>
 ;;; Copyright © 2018 Adam Massmann <massmannak@gmail.com>
 ;;; Copyright © 2018 Gabriel Hondet <gabrielhondet@gmail.com>
+;;; Copyright © 2020 Pierre Neidhardt <mail@ambrevar.xyz>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -31,7 +32,7 @@
   #:use-module (gnu packages)
   #:use-module ((guix licenses)
                 #:select (gpl2+ lgpl2.0+ lgpl2.1+ lgpl3+ asl2.0 bsd-3
-                          cc-by-sa4.0 non-copyleft))
+                          cc-by-sa4.0 non-copyleft expat))
   #:use-module (guix packages)
   #:use-module (guix download)
   #:use-module (guix git-download)
@@ -394,7 +395,7 @@ implementation techniques and as an expository tool.")
 (define-public racket
   (package
     (name "racket")
-    (version "7.3")
+    (version "7.6")
     (source (origin
               (method url-fetch)
               (uri (list (string-append "http://mirror.racket-lang.org/installers/"
@@ -404,7 +405,7 @@ implementation techniques and as an expository tool.")
                           version "/racket-" version "-src.tgz")))
               (sha256
                (base32
-                "0h6072njhb87rkz4arijvahxgjzn8r14s4wns0ijvxm89bg136yl"))
+                "0yagy7qrnz96gwafnj3whh2vs54788k1ci3vkm100h68gsw638b8"))
               (patches (search-patches
                         "racket-store-checksum-override.patch"))))
     (build-system gnu-build-system)
@@ -502,14 +503,15 @@ implementation techniques and as an expository tool.")
        ("sqlite" ,sqlite)
        ("unixodbc" ,unixodbc)
        ("libedit" ,libedit)))
-    (home-page "http://racket-lang.org")
+    (home-page "https://racket-lang.org")
     (synopsis "Implementation of Scheme and related languages")
     (description
      "Racket is an implementation of the Scheme programming language (R5RS and
 R6RS) and related languages, such as Typed Racket.  It features a compiler and
 a virtual machine with just-in-time native compilation, as well as a large set
 of libraries.")
-    (license lgpl2.0+)))
+    ;; https://download.racket-lang.org/license.html
+    (license (list lgpl3+ asl2.0 expat))))
 
 (define-public gambit-c
   (package