lz4 compressed wasm with ``-s SINGLE_FILE=1``

It would be cool, if emscripten provided the option to compress a wasm binary with LZ4 before base64-encoding and embedding it via ``-s SINGLE_FILE=1``.

Context: The solidity compiler https://github.com/ethereum/solidity has been publishing js/wasm binaries built with ``-s SINGLE_FILE=1`` for a while now. However, the binaries have grown to over 20MB in size and require a lot of bandwidth and long loading times. We realized that lz4 compressing the wasm binary before base64 encoding will reduce the size to ~8MB and loading times actually become *faster*, since base64 decoding is slow in comparison.
So we're working on doing this manually, but we were wondering, if this may be something that's generally useful and may be a nice feature in emscripten itself. (Especially since we realized that you support something very similar with ``LZ4 = 1`` already, just not applied to the embedded wasm binary)