Fetching TIC-80 submodules currently downloads all of duktape releases ever made because it includes https://github.com/svaarala/duktape-releases.git as a submodule (and submodules do a full clone by default).

Options:

a) CMake's FetchContent can be used instead to download only the latest release.
b) .gitmodules can be configured to shallow-clone the duktape submodule. https://stackoverflow.com/a/17692710/181228