If a project being built with ngtsc has no templates to check, then ngtsc
previously generated an empty typecheck file. This seems to trigger some
pathological behavior in TS where the entire user program is re-checked,
which is extremely expensive. This likely has to do with the fact that the
empty file is not considered an ES module, meaning the module structure of
the program has changed.
This commit causes an export to be produced in the typecheck file regardless
of its other contents, which guarantees that it will be an ES module. The
pathological behavior is avoided and template type-checking is fast once
again.
PR Close#31922
82b97280f3