keystone: make sure dylib's install name is correct on darwin

Using @rpath leads to problems later on, e.g. when linking against
haskellPackages.heystone which in turn links against keystone itself. As
soon as different rpaths/libdirs are in play, things fall apart.

pkgs/development/libraries/keystone/default.nix

@@ -3,6 +3,7 @@
 , pkg-config
 , cmake
 , python3
+, fixDarwinDylibNames
 }:
 
 stdenv.mkDerivation rec {
@@ -25,6 +26,9 @@ stdenv.mkDerivation rec {
     pkg-config
     cmake
     python3
+  ] ++ lib.optionals stdenv.hostPlatform.isDarwin [
+    # TODO: could be replaced by setting CMAKE_INSTALL_NAME_DIR?
+    fixDarwinDylibNames
   ];
 
   meta = with lib; {