emerge from ebuild in overlay failed (ninja error)

[tariella]

I tried emerging version 2.1.0 from the ebuild.

It fails with USE flags gtk2 and/or gtk3 in any combination.

The emerge error is:
ninja -v -j8 -l0 failed

error messages from the emerge log in detail:
../spacefm-2.1.0/src/settings.c:4657:19: error: assignment to ‘GtkWidget *’ {aka ‘struct _GtkWidget *’} from incompatible pointer type ‘PtkFileBrowser *’ [-Wincompatible-pointer-types]
4657 | dlgparent = set->browser;
| ^
../spacefm-2.1.0/src/settings.c: In function ‘xset_design_job’:
../spacefm-2.1.0/src/settings.c:5050:41: error: passing argument 1 of ‘gtk_widget_get_toplevel’ from incompatible pointer type [-Wincompatible-pointer-types]
5050 | parent = gtk_widget_get_toplevel(set->browser);
| ~~~^~~~~~~~~
| |
| PtkFileBrowser *

../spacefm-2.1.0/src/settings.c:6877:12: error: assignment to ‘GtkWidget *’ {aka ‘struct _GtkWidget *’} from incompatible pointer type ‘PtkFileBrowser *’ [-Wincompatible-pointer-types]
6877 | parent = set->browser;
| ^

../spacefm-2.1.0/src/mime-type/mime-action.c:588:29: error: passing argument 1 of ‘apps_dir_foreach’ from incompatible pointer type [-Wincompatible-pointer-types]
588 | return apps_dir_foreach(_locate_desktop_file, NULL, (void*)desktop_id);
| ^~~~~~~~~~~~~~~~~~~~
| |
| char * (*)(const char *, const char *, const void *)

The errors all seem to be related to -Wincompatible-pointer-types.