lilypond: fix build with clang21

pkgs/by-name/li/lilypond-unstable/package.nix

@@ -14,6 +14,8 @@ lilypond.overrideAttrs (
       hash = "sha256-UFuL8TZ7uLZhXgFoMGxAye04dNcvrw1gqQMOnE4P2fc=";
     };
 
+    patches = [ ];
+
     passthru.updateScript = writeScript "update-lilypond-unstable" ''
       #!/usr/bin/env nix-shell
       #!nix-shell -i bash -p common-updater-scripts curl

pkgs/by-name/li/lilypond/package.nix

@@ -41,6 +41,7 @@
     ]
   ),
   writeScript,
+  fetchpatch2,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -78,6 +79,18 @@ stdenv.mkDerivation (finalAttrs: {
       --replace-fail "mem=mf2pt1" "mem=$PWD/mf/mf2pt1"
   '';
 
+  patches = [
+    # fixes #475503
+    # distilled version of https://gitweb.git.savannah.gnu.org/gitweb/?p=lilypond.git;a=commit;h=f2192eb294e
+    # so, remove once that commit reaches a stable release
+    (fetchpatch2 {
+      name = "fix-clang-21-build.patch";
+      url = "https://cgit.freebsd.org/ports/plain/print/lilypond/files/patch-lily_include_smobs.hh?id=58bab68c706086774b17dcacc61c8fd37ecc8a15";
+      extraPrefix = ""; # adds old/new prefixes to process properly in patchPhase
+      hash = "sha256-nT8+nYU+m6lLTvHEvSIpG/yAwy1Omb6+4Z+NGwEVE4Q=";
+    })
+  ];
+
   strictDeps = true;
 
   depsBuildBuild = [