win32: Enable --werror in CI

5 jobs for win32-enable-werror in 18 minutes and 59 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #304722
fedora-x86_64

00:03:48

passed #304723
win32
msys2-mingw32

00:18:59

 
  Flatpak
manual #304724
allowed to fail manual
flatpak-manual:demo
manual #304726
allowed to fail manual
flatpak-manual:icon-browser
manual #304725
allowed to fail manual
flatpak-manual:widget-factory