NFC: Clean up runtime comments
Updating the todo list comments.
- Windows builds are already using the runtime build system to build
the runtimes so we can remove that from the todo list.
- The Android SDK on Windows is currently cross-compiled with the new
runtime build.
- Catalyst builds have been going for a bit now, generating the
necessary bits.
- We moved things to a nested swiftmodule structure, which installs the
entire directory, containing all of the emitted products.
The Glibc Linux builds should be coming soon.
We still have embedded to work on.
