There's a proposed standard for embedding DWARF debug info in WASM binaries [1], which at least Chrome already supports. This is the same format native executables use, so it should put wasm ahead of other VMs in terms of source language independence. Dwarf seems to be the best thing we have, even if it's not renowned for its ease of use.

[1] https://yurydelendik.github.io/webassembly-dwarf/