Though, this does mean that in language runtimes that don’t want to pull in native libraries (because the runtime is trying to ensure some guarantee like soft-realtime or fault-tolerance), libicu can’t be linked, so the runtime actually has to do the same thing it does, if it wants to have efficient Unicode lookup to the level that people expect: ship a copy of the database files from Unicode.org with the source, and convert them into source-code representations of decision-tree functions.
The language I’m most familiar with, Elixir, employs this strategy to support Unicode; see e.g. https://github.com/elixir-lang/elixir/blob/master/lib/elixir...