Don't allow saving over read-only files

BUGS: 440986
4 jobs for !480 with work/aacid/no_overwrite_readonly_files in 27 minutes and 43 seconds (queued for 43 minutes and 55 seconds)
latest detached
Status Name Job ID Coverage
  Build
passed build_clazy_clang_tidy #131360

00:11:34

passed build_ubuntu_20_04 #131359

00:06:21

passed clang_format #131361

00:01:25

passed linux kf5-qt5 qt5.15 #131358

00:08:22

46.0%