gtk4-query-immodules: command not found

[Stefan Salewski <mail ssalewski de>]

Following GTK4 install into /opt/gtk from 
https://developer.gnome.org/gtk4/3.93/gtk-building.html

I get for last step "ninja install"

Running custom install script '/opt/gtk+-3.93.0/build-aux/meson/post-
install.sh 4.0 4.0.0 /opt/gtk/lib64 /opt/gtk/share'
Compiling GSettings schemas...
Updating desktop database...
Updating icon cache...
Updating input method modules cache...
/opt/gtk+-3.93.0/build-aux/meson/post-install.sh: line 20: gtk4-query-
immodules: command not found
Failed to run install script '/opt/gtk+-3.93.0/build-aux/meson/post-
install.sh 4.0 4.0.0 /opt/gtk/lib64 /opt/gtk/share'
FAILED: meson-install 
/usr/bin/python3.5 /usr/lib/python-exec/python3.5/meson --internal
install /opt/gtk+-3.93.0/builddir/meson-private/install.dat
ninja: build stopped: subcommand failed.

I guess this may be the reason for that I get only tiny default fonts
for gtk4 apps launched under gnome3 wayland.

What may be the best way to fix this issue?