openat via /proc, this technique can still fail, but
only in extreme conditions, e.g., when the working
directory cannot be saved (i.e. save_cwd fails) --
- and that happens only on Linux only when "." is unreadable
+ and that happens on Linux only when "." is unreadable
and the CWD would be longer than PATH_MAX.
FIXME: once Linux kernel openat support is well established,
replace the above open call and this entire if/else block