x11-toolkits/gtk40: unbreak on FreeBSD < 12

FAILED: tools/gtk4-encode-symbolic-svg
cc -o tools/gtk4-encode-symbolic-svg tools/gtk4-encode-symbolic-svg.p/encodesymbolic.c.o -Wl,--as-needed -Wl,--no-undefined -Wl,-O1 -Wl,--start-group -lexecinfo -fstack-protector-strong gtk/libgtk.a gtk/css/libgtk_css.a gdk/libgdk.a gdk/broadway/libgdk-broadway.a gdk/wayland/libgdk-wayland.a gdk/wayland/cursor/libwayland+cursor.a gdk/x11/libgdk-x11.a gsk/libgsk.a -Wl,-Bsymbolic -Wl,-z,relro -Wl,-z,now -Wl,--export-dynamic /usr/local/lib/libgmodule-2.0.so -pthread /usr/local/lib/libglib-2.0.so /usr/local/lib/libintl.so /usr/local/lib/libgobject-2.0.so /usr/local/lib/libgio-2.0.so /usr/local/lib/libpangocairo-1.0.so /usr/local/lib/libpango-1.0.so /usr/local/lib/libharfbuzz.so /usr/local/lib/libcairo.so -lpthread /usr/local/lib/libfribidi.so /usr/local/lib/libcairo-gobject.so /usr/local/lib/libfontconfig.so /usr/local/lib/libfreetype.so /usr/local/lib/libgdk_pixbuf-2.0.so /usr/local/lib/libepoxy.so -lm /usr/local/lib/libgraphene-1.0.so /usr/local/lib/libpangoft2-1.0.so /usr/local/lib/libXi.so /usr/local/lib/libX11.so /usr/local/lib/libxkbcommon.so /usr/local/lib/libwayland-client.so /usr/local/lib/libwayland-egl.so /usr/local/lib/libXrender.so /usr/local/lib/libXext.so /usr/local/lib/libXcursor.so /usr/local/lib/libXdamage.so /usr/local/lib/libXfixes.so /usr/local/lib/libXcomposite.so /usr/local/lib/libXrandr.so /usr/local/lib/libXinerama.so /usr/local/lib/libcairo-script-interpreter.so -Wl,--end-group
/usr/bin/ld: undefined reference to symbol `g_module_symbol' (try adding -lgmodule-2.0)
/usr/local/lib/libgmodule-2.0.so: could not read symbols: Bad value
cc: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.

• Error code 1

Reported by: pkg-fallout