bootstrap: Avoid gnulib operations if not needed * build-aux/bootstrap: Remove unused variable gnulib_mk. Set $gnulib_extra_files early so it can be overridden in .conf. Remove redundant --import flag from $gnulib_tool_options. Set $use_gnulib to false if no gnulib modules or files are needed. If $use_gnulib is false, don't do anything related to gnulib. A lot of this is just whitespace (indentation) changes.

Please create and read the docs with

  $ cd doc
  $ make gnulib.html
  $ xdg-open gnulib.html

or read the online manual at

  https://www.gnu.org/software/gnulib/manual/gnulib.html