Adding directories to PATH:
PATH += /home/diego/Desktop/emsdk
PATH += /home/diego/Desktop/emsdk/upstream/emscripten
PATH += /home/diego/Desktop/emsdk/node/14.15.5_64bit/bin

Setting environment variables:
PATH = /home/diego/Desktop/emsdk:/home/diego/Desktop/emsdk/upstream/emscripten:/home/diego/Desktop/emsdk/node/14.15.5_64bit/bin:/home/diego/geckodriver:/home/diego/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
EMSDK = /home/diego/Desktop/emsdk
EM_CONFIG = /home/diego/Desktop/emsdk/.emscripten
EMSDK_NODE = /home/diego/Desktop/emsdk/node/14.15.5_64bit/bin/node
wasm-ld: error: duplicate symbol: lux::GAME_CONSTANTS
>>> defined in /tmp/emscripten_temp_bllbhzg_/main_0.o
>>> defined in /tmp/emscripten_temp_bllbhzg_/foo_1.o

wasm-ld: error: duplicate symbol: lux::operator<<(std::__2::basic_ostream<char, std::__2::char_traits<char> >&, lux::Position const&)
>>> defined in /tmp/emscripten_temp_bllbhzg_/main_0.o
>>> defined in /tmp/emscripten_temp_bllbhzg_/foo_1.o

wasm-ld: error: duplicate symbol: INPUT_CONSTANTS::DONE
>>> defined in /tmp/emscripten_temp_bllbhzg_/main_0.o
>>> defined in /tmp/emscripten_temp_bllbhzg_/foo_1.o

wasm-ld: error: duplicate symbol: INPUT_CONSTANTS::RESEARCH_POINTS
>>> defined in /tmp/emscripten_temp_bllbhzg_/main_0.o
>>> defined in /tmp/emscripten_temp_bllbhzg_/foo_1.o

wasm-ld: error: duplicate symbol: INPUT_CONSTANTS::RESOURCES
>>> defined in /tmp/emscripten_temp_bllbhzg_/main_0.o
>>> defined in /tmp/emscripten_temp_bllbhzg_/foo_1.o

wasm-ld: error: duplicate symbol: INPUT_CONSTANTS::UNITS
>>> defined in /tmp/emscripten_temp_bllbhzg_/main_0.o
>>> defined in /tmp/emscripten_temp_bllbhzg_/foo_1.o

wasm-ld: error: duplicate symbol: INPUT_CONSTANTS::CITY
>>> defined in /tmp/emscripten_temp_bllbhzg_/main_0.o
>>> defined in /tmp/emscripten_temp_bllbhzg_/foo_1.o

wasm-ld: error: duplicate symbol: INPUT_CONSTANTS::CITY_TILES
>>> defined in /tmp/emscripten_temp_bllbhzg_/main_0.o
>>> defined in /tmp/emscripten_temp_bllbhzg_/foo_1.o

wasm-ld: error: duplicate symbol: INPUT_CONSTANTS::CELL_COOLDOWN
>>> defined in /tmp/emscripten_temp_bllbhzg_/main_0.o
>>> defined in /tmp/emscripten_temp_bllbhzg_/foo_1.o
emcc: error: '/home/diego/Desktop/emsdk/upstream/bin/wasm-ld -o main.wasm /tmp/emscripten_temp_bllbhzg_/main_0.o /tmp/emscripten_temp_bllbhzg_/foo_1.o -L/home/diego/Desktop/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten -lGL -lal -lhtml5 -lc -lcompiler_rt -lc++-noexcept -lc++abi-noexcept -ldlmalloc -lc_rt_wasm -lsockets -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr --allow-undefined --strip-debug --export main --export emscripten_stack_get_end --export emscripten_stack_get_free --export emscripten_stack_init --export stackSave --export stackRestore --export stackAlloc --export __wasm_call_ctors --export fflush --export __errno_location --export malloc --export free --export-if-defined=__start_em_asm --export-if-defined=__stop_em_asm --export-table -z stack-size=5242880 --initial-memory=16777216 --no-entry --max-memory=16777216 --global-base=1024' failed (returned 1)