Fixes a test failure introduced in
189525412e.
* guix/progress.scm: Autoload (guix build syscalls).
* tests/gexp.scm ("gexp->derivation, store copy"): Add (guix build
syscalls) to the list of imported modules. Use ‘with-imported-modules’
rather than #:modules.
Change-Id: I8d3fe90f564ef4b1a340f34cee6c08a741f7b836