lilypond-with-fonts: fix lilypond not finding its libraries

Fixes #140152. The fix is inspired by how lilypond-with-fonts was
packaged in v18.09.

pkgs/misc/lilypond/with-fonts.nix

@@ -1,4 +1,4 @@
-{ lib, lndir, symlinkJoin, makeWrapper
+{ lib, symlinkJoin, makeWrapper
 , lilypond, openlilylib-fonts
 }:
 
@@ -8,11 +8,10 @@ lib.appendToName "with-fonts" (symlinkJoin {
   paths = [ lilypond ] ++ openlilylib-fonts.all;
 
   nativeBuildInputs = [ makeWrapper ];
-  buildInputs = [ lndir ];
 
   postBuild = ''
     for p in $out/bin/*; do
-        wrapProgram "$p" --set LILYPOND_DATADIR "$datadir"
+        wrapProgram "$p" --set LILYPOND_DATADIR "$out/share/lilypond/${lilypond.version}"
     done
   '';
 })