libjxl: Move brotli and libhwy to propagatedBuildInputs

pkg-config dependencies aren't specified using store paths so
they need to be propagated manually

pkgs/development/libraries/libjxl/default.nix

@@ -78,10 +78,8 @@ stdenv.mkDerivation rec {
   # conclusively in its README or otherwise; they can best be determined
   # by checking the CMake output for "Could NOT find".
   buildInputs = [
-    brotli
     giflib
     gperftools # provides `libtcmalloc`
-    libhwy
     libjpeg
     libpng
     libwebp
@@ -89,6 +87,11 @@ stdenv.mkDerivation rec {
     zlib
   ];
 
+  propagatedBuildInputs = [
+    brotli
+    libhwy
+  ];
+
   cmakeFlags = [
     # For C dependencies like brotli, which are dynamically linked,
     # we want to use the system libraries, so that we don't have to care about