tools: add convenience script for repackaging demangling sources from llvm-project
tools: add convenience script for repackaging demangling sources from llvm-project

Ultimately, this will be more portable and handle Rust mangling,
among other things.

Bug: 204297290
Change-Id: I4f8afb3b5ef0a1162ff15edd7b929f374071d443
google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto