gnu: libicns: Fix cross-compiling to riscv64.

* gnu/packages/image.scm (libicns)[arguments]: When cross-compiling to
riscv64, add phase to update-config-scripts.
[native-inputs]: When cross-compiling to riscv64, add config.

Signed-off-by: Efraim Flashner <efraim@flashner.co.il>

gnu/packages/image.scm

@@ -595,6 +595,25 @@ maximum quality factor.")
                (base32
                 "1hjm8lwap7bjyyxsyi94fh5817xzqhk4kb5y0b7mb6675xw10prk"))))
     (build-system gnu-build-system)
+    (arguments
+     (if (and (target-riscv64?)
+              (%current-target-system))
+       (list #:phases
+             #~(modify-phases %standard-phases
+                 (add-after 'unpack 'update-config-scripts
+                   (lambda* (#:key native-inputs inputs #:allow-other-keys)
+                     (for-each (lambda (file)
+                                 (install-file
+                                   (search-input-file
+                                     (or native-inputs inputs)
+                                     (string-append "/bin/" file)) "."))
+                               '("config.guess" "config.sub"))))) )
+       '()))
+    (native-inputs
+     (if (and (target-riscv64?)
+              (%current-target-system))
+       (list config)
+       '()))
     (inputs
      (list libpng jasper))
     (home-page "https://icns.sourceforge.io/")