ledit: fix broken executable

Prior to this change ledit failed with a 127 exit code:

    $ ledit
    no bytecode file specified
    $ echo hello | ledit cat
    the file 'cat' has not the right magic number: expected Caml1999X036

Upstream builds ledit with `ocamlc -custom`, which attaches the program
to the end of the executable. Stripping drops it again.
With dontStrip the program stays in place:

    $ echo hello | ledit cat
    hello
    hello

Signed-off-by: Matthias J. Kannwischer <matthias@zerorisc.com>

pkgs/by-name/le/ledit/package.nix

@@ -22,6 +22,8 @@ stdenv.mkDerivation {
 
   strictDeps = true;
 
+  dontStrip = true;
+
   nativeBuildInputs = with ocamlPackages; [
     ocaml
     findlib
@@ -33,6 +35,15 @@ stdenv.mkDerivation {
     camlp-streams
   ];
 
+  doInstallCheck = true;
+
+  installCheckPhase = ''
+    runHook preInstallCheck
+    echo hello | $out/bin/ledit -h /dev/null cat > ledit-check.out
+    grep -q hello ledit-check.out
+    runHook postInstallCheck
+  '';
+
   meta = {
     homepage = "http://pauillac.inria.fr/~ddr/ledit/";
     description = "Line editor, allowing to use shell commands with control characters like in emacs";