Mirror Hare's os env surface: getenvs() builds an owned []str of
NAME=VALUE entries from the rt_envp table (platform_environ.ha:41),
and getenv iterates it (environ.ha:32) so there is exactly one env
walker. strings.dup is unusable here -- lib/strings imports os, so os
importing strings would cycle; the owned copy is inlined (dup.ha:7).
test_getenvs_entries pins the []str shape non-vacuously.
Hojun-Cho
93b671808c