based on changes from upstream rules_svelte
Their code was using run_node() instead of ctx.actions.run(), which
seems to create a new worker for every CPU core, instead of respecting
the standard limit of 4.
Svelte 3.25.0 and onwards bundle compiler.mjs, which seems to be
preferentially used over the .js file. Presumably this is only breaking
on Windows due to the lack of a sandbox. Resolve by explicitly requesting
the .js file.
