orpie: fix build

pkgs/applications/misc/orpie/default.nix

@@ -13,12 +13,10 @@ ocamlPackages.buildDunePackage rec {
     sha256 = "1rx2nl6cdv609pfymnbq53pi3ql5fr4kda8x10ycd9xq2gc4f21g";
   };
 
+  patches = [ ./prefix.patch ];
+
   preConfigure = ''
-    patchShebangs scripts
-    substituteInPlace scripts/compute_prefix \
-      --replace '"topfind"' \
-      '"${ocamlPackages.findlib}/lib/ocaml/${ocamlPackages.ocaml.version}/site-lib/topfind"'
-    export PREFIX=$out
+    substituteInPlace src/orpie/install.ml.in --replace '@prefix@' $out
   '';
 
   buildInputs = with ocamlPackages; [ curses camlp5 num gsl ];

pkgs/applications/misc/orpie/prefix.patch

@@ -0,0 +1,11 @@
+--- a/src/orpie/dune	2021-10-05 06:09:09.040120000 +0200
++++ b/src/orpie/dune	2021-10-05 06:10:06.568418512 +0200
+@@ -18,7 +18,7 @@
+ ; Support $PREFIX for overriding installation location
+ (rule
+   (targets install.ml)
+-  (action (run %{project_root}/scripts/compute_prefix subst %{deps} %{targets}))
++  (action (copy# %{deps} %{targets}))
+   (deps (file install.ml.in)))
+ 
+