Since 1.15.0-2 gzip uses slicc-kernel's process credentials (restoring an
owner as root works, any other user keeps its own) and ends by the signal it
sends itself (kill -TERM of its own pid, slicc-kernel ≥ 1.73.2). The output
of gzip -k/gunzip keeps the input's times on slicc-kernel ≥ 1.73.3 (#441:
earlier kernels reset an mtime set on an open file when gzip then changed its
owner, in the browser).