configury: don't bundle build-time larch macros.

* local.mk (bin_specl_SOURCES): A list of files used to build
bin/specl.
(dist_noinst_DATA): Append to this.
(bin/specl): Expand only $(bin_specl_SOURCES), not all of
$(dist_noinst_DATA).

Signed-off-by: Gary V. Vaughan <gary@gnu.org>