TODO: user-environment-hook

[宋文武]

Currently, (guix profiles) has code to build 'info-dir' for packages in profile.
As mentioned in TODO, IIUC, we should move the code to 'texinfo'.

Other usecases include:
* hicolor-icon-theme: use gtk-update-icon-cache to get 'icon-theme.cache'.
* shared-mime-info: use update-mime-database to get 'mime.cache'.
* desktop-file-utils: use update-desktop-database to get 'mimeinfo.cache'.
? glib: use glib-compile-schemas to get 'gschema.compiled'.

For schemas, it's always safe for packages in system profile,
but may broken for user profile:
  user had install package A
  user update the guix disto, A -> A' has incompatible schema change
  user now install package B' which depend on schema of A'
B' will crash if we have schemas from A and B'.

If we make A a propagated-inputs of B, dose A will be update to A' when
install B'?
If so, that's great, we can even get rid of glib-or-gtk-build-system.