I'm encountering a compile-time error when building the latest Emacs igc branch with the `--with-mps=yes' and `--with-xwidget' options:

igc.c:2459:5: error: no member named 'gc_header' in 'struct xwidget_view'; did you mean 'header'?

 2459 |     IGC_FIX12_HEADER (ss, &w->xv);

      |     ^

igc.c:1144:61: note: expanded from macro 'IGC_FIX12_HEADER'

 1144 |       igc_assert ((mps_addr_t) (*p) == (mps_addr_t) & (*p)->gc_header); \

      |                                                             ^

./xwidget.h:104:28: note: 'header' declared here

  104 |   struct vectorlike_header header;

      |                            ^

Please let me know if you need any additional information to investigate this issue.

Thanks.