Whilst clang reports a warning, gcc cannot compile libvips against the latest main branch of libjxl without the change in this PR, so we might want to backport this to 8.12 if there are going to be further 8.12.x releases.

clang:

../libvips/foreign/jxlsave.c:284:27: warning: 'JXL_TYPE_UINT32' is deprecated [-Wdeprecated-declarations]
                jxl->format.data_type = JXL_TYPE_UINT32;

gcc:

../libvips/foreign/jxlsave.c:185:2: error: case label does not reduce to an integer constant
  185 |  case JXL_TYPE_UINT32:
      |  ^~~~

argh, why did they remove the enum and break all downstream projects? Sure, I'll patch 8.12 too.