gnu: mes: Prepare for non-x86 architectures.

* gnu/packages/mes.scm (mes)[native-inputs]: Change i686-linux-binutils and
i686-linux-gcc conditional inclusion.

gnu/packages/mes.scm

@@ -60,7 +60,6 @@ (define-public nyacc
     (license (list gpl3+ lgpl3+))))
 
 (define-public mes
-  (let ((triplet "i686-unknown-linux-gnu"))
   (package
     (name "mes")
     (version "0.19")
@@ -78,13 +77,16 @@ (define-public mes
        ("nyacc" ,nyacc)))
     (native-inputs
      `(("guile" ,guile-2.2)
-         ,@(if (not (string-prefix? "i686-linux" (or (%current-target-system)
+       ,@(let ((target-system (or (%current-target-system)
                                   (%current-system))))
+           (cond
+            ((string-prefix? "x86_64-linux" target-system)
              ;; Use cross-compiler rather than #:system "i686-linux" to get
              ;; MesCC 64 bit .go files installed ready for use with Guile.
-               `(("i686-linux-binutils" ,(cross-binutils triplet))
+             `(("i686-linux-binutils" ,(cross-binutils "i686-unknown-linux-gnu"))
-                 ("i686-linux-gcc" ,(cross-gcc triplet)))
+               ("i686-linux-gcc" ,(cross-gcc "i686-unknown-linux-gnu"))))
-               '())
+            (else
+             '())))
        ("graphviz" ,graphviz)
        ("help2man" ,help2man)
        ("perl" ,perl)                 ; build-aux/gitlog-to-changelog
@@ -99,7 +101,7 @@ (define-public mes
 interpreter in C and a Nyacc-based C compiler in Scheme and is compatible with
 Guile.")
     (home-page "https://gnu.org/software/mes")
-      (license gpl3+))))
+    (license gpl3+)))
 
 (define-public mescc-tools
   (package