Pull the emscripten image then to compile wasm run:
docker run \
--rm \
-v $(pwd):/src \
-u $(id -u):$(id -g) \
emscripten/emsdk \
emcc movement.c -O3 -s EXPORT_ES6=1 -s USE_ES6_IMPORT_META=0 -s MODULARIZE=1 -s EXPORTED_FUNCTIONS="['_get_canvas_size', '_get_selection','_change_direction','_update_axis','_get_canvas_size', '_get_resize_ratio']" -o movement_wasm.js -O3