feat(exit): #136 expose exit api (#6)

wasm/build-scripts/build-ffmpeg.sh

@@ -22,6 +22,7 @@ FLAGS=(
   -s EXPORTED_FUNCTIONS="[_main, _proxy_main]"  # export main and proxy_main funcs
   -s EXTRA_EXPORTED_RUNTIME_METHODS="[FS, cwrap, ccall, setValue, writeAsciiToMemory]"   # export preamble funcs
   -s INITIAL_MEMORY=2146435072                  # 64 KB * 1024 * 16 * 2047 = 2146435072 bytes ~= 2 GB
+  --post-js wasm/post-js.js
   $OPTIM_FLAGS
 )
 echo "FFMPEG_EM_FLAGS=${FLAGS[@]}"

wasm/post-js.js

+Module["exit"] = exit;