[llvm] [lldb][bazel] Add PlatformWasm plugin library to the Bazel overlay (PR #209749)

[Jordan Rupprecht via llvm-commits]

rupprecht wrote:

> I left it out here, unless there's a desire to add it in.

I don't have any objection, but maybe we can land as-is in case @keith has any opinions.

https://github.com/llvm/llvm-project/pull/209749