We don't want to record the state of the file system at the start
of the compilation in the compiled files.
Consequently, we only add persistent modules to the env summary
if they have an observable action on the initial environment.
This is only the case if they shadow a non-persistent module of the
initially opened library (which can only be Stdlib currently).

Add missing -function-sections in Makefile in otherlibs

Fix #mod_use in toplevel

Ensure that distclean works in an unconfigured tree. At the end of the
build, ensure that no tracked files have been altered or untracked files
created and ensure that distclean removes all ignored files.