lilv: add meson options to include Nix and NixOS specific paths for the default lv2 plugin search (#346713)

pkgs/development/libraries/audio/lilv/default.nix

@@ -32,10 +32,19 @@ stdenv.mkDerivation rec {
   propagatedBuildInputs = [ lv2 ];
 
   mesonFlags = [
-    "-Ddocs=disabled"
+    (lib.mesonOption "docs" "disabled")
     # Tests require building a shared library.
     (lib.mesonEnable "tests" (!stdenv.hostPlatform.isStatic))
-  ];
+  ] # Add nix and NixOS specific lv2 paths
+    # The default values are from: https://github.com/lv2/lilv/blob/master/src/lilv_config.h
+    ++ lib.optional stdenv.isDarwin  (lib.mesonOption "default_lv2_path"
+      "~/.lv2:~/Library/Audio/Plug-Ins/LV2:"
+      + "/usr/local/lib/lv2:/usr/lib/lv2:"
+      + "/Library/Audio/Plug-Ins/LV2:"
+      + "~/.nix-profile/lib/lv2")
+    ++ lib.optional stdenv.isLinux  (lib.mesonOption "default_lv2_path"
+      "~/.lv2:/usr/local/lib/lv2:/usr/lib/lv2:"
+      + "~/.nix-profile/lib/lv2:/run/current-system/sw/lib/lv2");
 
   passthru = {
     tests = {