wasm-emscripten: add support for address sanitizer

In this commit, the --with-sanitizer option is forwarded to the configure script for VLC, but also intercepted so that the emcc call creating the plugin list can use the option as well.

It's necessary for now since the plugin list is not generated by automake yet, thus the call to emcc is not intercepted to add the sanitizer options added from VLC's configure.ac.