TODO: There are still direct references to specific version of Python in:
  - slapos component
  - bazel templates
  - nextcloud & theia SR

  This is required to support aarch64 systems.
  The edition of PYTHON_LIBS is probably wrong but it what made it work. In future, it would be
  better clean up it.

* now glib is built with our own pcre.
* libsigc++, glibmm, pangomm and atkmm are kept in older version because glibmm >= 2.46 requires C++11 compiler.

so that build will not fail if the directory was left during previous
builds.

Conflicts:
	stack/slapos.cfg