* guix/scripts/environment.scm (show-environment-options-help, %options): Add
'--emulate-fhs'.
(setup-fhs): New procedure. Setup for the Filesystem Hierarchy Standard (FHS)
container. Defines and uses FHS-SYMLINKS and LINK-CONTENTS to create FHS
expected directories and creates /etc/ld.so.conf.
(launch-environment): Add 'emulate-fhs?' key and implement it to set $PATH and
generate /etc/ld.so.cache before calling COMMAND.
(launch-environment/container): Add 'emulate-fhs?' and 'setup-hook' keys and
implement them. Define and use FHS-MAPPINGS, to set up additional bind mounts
in the container to follow FHS expectations.
(guix-environment*): Add glibc-for-fhs to the container packages when
'emulate-fhs?' key is in OPTS.
* doc/guix.texi (Invoking guix shell): Document '--emulate-fhs'.
(Invoking guix environment): Document '--emulate-fhs'.
* tests/guix-environment-container.sh: Add tests for '--emulate-fhs'.
Co-authored-by: Ludovic Courtès <ludo@gnu.org>
