Add failing test: stat/lstat are weak symbols in libc, so LD_PRELOAD cannot override them in the same way
Override __lxstat and __xstat, not lstat/xstat which are un-overridable weak symbols
Oops: Must not report outputs as inputs or undelayed inputs get confused for meddled inputs
fs_override: Oops: root_filter didn't capture references to directory itself
KNOWN_ISSUES
Add special handling of 'stat' inputs. Do not require children of directory due to stat-of-directory (see KNOWN_ISSUES). Also compare stat's essence only. Directories do not compare size.
PosixInstances -> Posix.Instances
Add Lib.Posix.FileType
Only directories compare partial stat. Everything else compares as much of stat as possible
Oops: directory input access that's upgraded to full [and thus may cause buildsome to meddle with the directory's stats] remembers the new directory stat after the contained files' generation, rather than before