nanobsd: Fix regressions from last cleanup

c99bb5747f5e changed ( ) grouping into { }, but in these cases we chdir
and depended on the subshell not changing it for the caller. Restore the
old behavior. It seems to work w/o this change, true, but the old code
was intentionally like this.

Fixes: c99bb5747f5e
Sponsored by: Netflix