add_build_file

#import "File";

#run {
    path := tprint("%/extra.jai", #filepath);
    write_entire_file(path, "extra :: 1;");
    w := compiler_create_workspace("from file");
    options := get_build_options(w);
    options.output_type = .NO_OUTPUT;
    set_build_options(options, w);
    add_build_file(path, w);
}

main :: () {}

Doesn't run in the browser (skipped on wasm).