touch -r: dangling symlink reference is accepted

[sylvestre]

Component

touch

Description

When touch is asked to follow symlinks (default), stat() falls back from fs::metadata() to
fs::symlink_metadata() on any error.

fs::metadata(path).or_else(|_| fs::symlink_metadata(path))

This means touch -r <ref> <dst> will silently accept a dangling symlink reference and use the symlink’s
own timestamps, instead of erroring like GNU.

Test / Reproduction Steps

mkdir -p /tmp/touch-audit
cd /tmp/touch-audit
ln -s /nope ref
rm -f out

# uutils: succeeds, creates "out"
# GNU: fails (reference is inaccessible)
touch -r ref out; echo "exit:$?"; ls -la out

Impact

Hides real failures for -r/--reference and can make scripts behave as if the reference file was valid.
Also breaks GNU compatibility.

[dshemetov]

Hope it's ok I took a stab at this one in the PR above. Open to suggestions!