emscripten miniscript.js errors with fix

[Kelbie]

OS: Macos

So I was trying to build the miniscript.js using emscripten which didn't work initially and gave an error of TypeError: Module.asm.S is undefined. I landed on this issue which fixed my problem, basically you just need to alter the Makefile to:

miniscript.js: $(HEADERS) $(SOURCES) js_bindings.cpp
    em++ -O3 -g0 -Wall -std=c++11 -fno-rtti -flto -Ibitcoin $(SOURCES) js_bindings.cpp -s WASM=1 -s FILESYSTEM=0 -s ENVIRONMENT=web -s DISABLE_EXCEPTION_CATCHING=0 -s EXPORTED_FUNCTIONS='["_miniscript_compile","_miniscript_analyze","_malloc","_free"]' -s EXTRA_EXPORTED_RUNTIME_METHODS='["cwrap","UTF8ToString"]' -o miniscript.js -s WASM=0 --memory-init-file 0

Note the -s WASM=0 --memory-init-file 0 at the end.

I don't fully understand what this does so I didn't feel comfortable putting it into a pull request but thought it should be reported on but I would gladly turn this into a pull request if you sign off on it so let me know what you think.