util/create_tmpfile: set restrictive umask for these files
util/create_tmpfile: set restrictive umask for these files

Even if the file is removed right away, a race with someone using inotify
is definitely possible, so play safe and restrict umask for our tmpfiles

Found through static analysis.

swaywm/wlroots,ascent12/wlroots,swaywm/wlroots,SirCmpwn/wlroots,ascent12/wlroots