harfbuzz: add flag to correctly install CMake files

Similar to how we already set -DKDE_INSTALL_CMAKEPACKAGEDIR in CMake
builds, Harfbuzz now uses -Dcmakepackagedir to correctly handle both
Nixpkgs split outputs and relocatable installations.

See https://github.com/harfbuzz/harfbuzz/pull/4370.

pkgs/development/libraries/harfbuzz/default.nix

@@ -63,6 +63,7 @@ stdenv.mkDerivation (finalAttrs: {
     (lib.mesonEnable "graphite" withGraphite2)
     (lib.mesonEnable "icu" withIcu)
     (lib.mesonEnable "introspection" withIntrospection)
+    (lib.mesonOption "cmakepackagedir" "${placeholder "dev"}/lib/cmake")
   ];
 
   depsBuildBuild = [