Possible workaround (not that mit-scheme works on aarch64 then, but at least guix does):

diff --git a/gnu/packages/scheme.scm b/gnu/packages/scheme.scm
index c7ab00380..25852d2af 100644
--- a/gnu/packages/scheme.scm
+++ b/gnu/packages/scheme.scm
@@ -70,12 +70,7 @@
   #:use-module (ice-9 match))
 
 (define (mit-scheme-source-directory system version)
-  (string-append "mit-scheme-"
-                 (if (or (string-prefix? "x86_64" system)
-                         (string-prefix? "i686" system))
-                     ""
-                     "c-")
-                 version))
+  (string-append "mit-scheme-" version))
 
 (define-public mit-scheme
   (package
@@ -173,7 +168,7 @@
                                 ("i686-linux"
                                  (string-append version "-i386"))
                                 (_
-                                 (string-append "c-" version)))
+                                 version))
                               ".tar.gz"))
           (sha256
            (match (%current-system)
@@ -182,7 +177,10 @@
                "03m7cc035w3avs91j2pcz9f15ssgvgp3rm045d1vbydqrkzfyw8k"))
              ("i686-linux"
               (base32
-               "05sjyz90xxfnmi87qv8x0yx0fcallnzl1dciygdafp317pn489is"))))))))
+               "05sjyz90xxfnmi87qv8x0yx0fcallnzl1dciygdafp317pn489is"))
+             (_
+              (base32
+               "18kllckm3iky59wk3nvx41kfn56lpp468savvrk41agjza2hqqhy"))))))))
 
     ;; Fails to build on MIPS, see <http://bugs.gnu.org/18221>.
     ;; Also, the portable C version of MIT/GNU Scheme did not work in time for