guile: allow libunistring and Readline to be found on OpenSolaris

pkgs/development/interpreters/guile/default.nix

@@ -82,12 +82,19 @@
 //
 
 (stdenv.lib.optionalAttrs stdenv.isSunOS {
-  # Make sure the right <gmp.h> is found, and not the incompatible
-  # /usr/include/mp.h from OpenSolaris.  See
-  # <https://lists.gnu.org/archive/html/hydra-users/2012-08/msg00000.html>
-  # for details.
   # TODO: Move me above.
-  configureFlags = [ "--with-libgmp-prefix=${gmp}" ];
+  configureFlags =
+    [
+      # Make sure the right <gmp.h> is found, and not the incompatible
+      # /usr/include/mp.h from OpenSolaris.  See
+      # <https://lists.gnu.org/archive/html/hydra-users/2012-08/msg00000.html>
+      # for details.
+      "--with-libgmp-prefix=${gmp}"
+
+      # Same for these (?).
+      "--with-libreadline-prefix=${readline}"
+      "--with-libunistring-prefix=${libunistring}"
+    ];
 })
 
 //