Pacify gcc -Wunused-function on Ubuntu 18.04.3

This improves on 2019-12-25T20:01:07Z!eggert@cs.ucla.edu,
by fixing a GCC warning on Ubuntu 18.04.3
“‘x_get_net_workarea’ defined but not used”.
* src/xfns.c (x_get_net_workarea) [!USE_GTK]: Do not define.
2 jobs for emacs-27 in 86 minutes and 3 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Test
failed #4638
test-all

01:26:03

passed #4639
test-filenotify-gio

00:58:46

 
Name Stage Failure
failed
test-all Test
Makefile:319: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:294: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:959: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1