* guix/import/texlive.scm (tlpdb): Store "execute" entries.
(tlpdb->package): Add #:CREATE-FORMATS argument when there is an AddFormat
execute action.
* tests/texlive.scm (%fake-tlpdb): Add test data.
("texlive->guix-package, with TeX format"):
("texlive->guix-package, execute but no TeX format"): New tests.