tests: Make sure file time changes seconds

Otherwise fontconfig might report that no update was necessary, and
g-s-d would print a different message, resulting in a test failure.
6 jobs for benzea/ci-fixes in 3 minutes and 9 seconds (queued for 6 seconds)
Status Name Job ID Coverage
  Build
passed build #1402934

00:00:51

 
  Test
passed test #1402935

00:02:17

 
  Manual
manual asan #1402936
asan allowed to fail manual
manual msan #1402939
allowed to fail manual
manual tsan #1402937
allowed to fail manual
manual ubsan #1402938
allowed to fail manual