[clang] [clang-repl] Support wasm execution (PR #86402)

[Vassil Vassilev via cfe-commits]

vgvassilev wrote:

Hi @AaronBallman, we need some leadership here.

This pull request teaches clang-repl to work inside a browser. It enables webassembly [xeus-cpp](https://github.com/compiler-research/xeus-cpp) (through clang-repl) which connects to the JupyterLite infrastructure. This change (actually an older version of it) enables execution of C++ in a browser. Here is an example https://wasmdemo.argentite.me/

This way we can enable in JupyterLite system programming with C/C++ which can be transformative for education in system programming as it only requires a browser not a cloud service.

Unfortunately, this PR cannot be tested in the current testing infrastructure in llvm because it needs a browser to provide a proper execution environment. If we move forward here that would unblock work on the other end of the infrastructure.

https://github.com/llvm/llvm-project/pull/86402