system: update checkout.

Submodule system 067216c..5f082f1:
  > system/essential/verbatim-files: systemd: update to systemd-215.
  > framework: update checkout.
  > framework: update checkout.
  > framework: update checkout.
  > framework: update checkout.
helper-symlink-stages.sh: update path to my work tree.
helper-symlink-stages.sh: m-a-s: fix behavior when $1 is not given; in this case, repair all symlinks in cwd.
profiles: regroup, assuming that stage lists from different profiles are sort-merged.
functions.sh: support running only from cwd; remove the never-used finding logic.
functions/runner: add a custom stage lister with support for merging stage lists between profiles.
install.sh: rewrite using getopt, allowing to configure the installation process.