Thanks to Ludovic Courtès <ludo@gnu.org> for patching this in the Guix
package definition.
* build-aux/guile.am (moddir, ccachedir): Use the 'site' directories.
* build-aux/guile-rules.am: Delete file.
* build-aux/guile.am: New file.
* .gitignore: Do not ignore it.
* Makefile.am: Adapt variable names to the new file.