undefined symbols for fetch api even with FETCH = 1

Error log:
```
cmd.exe /C "cd . && C:\Users\daego\Desktop\Projects\Light.vn-multi\core\build-em\..\..\..\emsdk\upstream\emscripten\em++.bat -s WASM=1 -Wno-warn-absolute-paths -s USE_PTHREADS=1 -s PTHREAD_POOL_SIZE=8 -s FETCH=1 -s LLD_REPORT_UNDEFINED -Wno-unknown-pragmas -DNDEBUG -O3 -O3 -DNDEBUG -s WASM=1 -O3 --llvm-lto 1 _deps/csvparser-build/programs/CMakeFiles/csv_info.dir/csv_info.cpp.o -o ..\bin-Emscripten-Release\csv_info.js ../bin-Emscripten-Release/csv.bc && cd ."
emcc:WARNING: --llvm-lto ignored when using llvm backend
error: undefined symbol: _emscripten_fetch_delete_cached_data (referenced by top-level compiled C/C++ code)
warning: To disable errors for undefined symbols use `-s ERROR_ON_UNDEFINED_SYMBOLS=0`
```
As you can see, I've defined fetch = 1. According to the docs here this should be sufficient yet isn't.

https://emscripten.org/docs/api_reference/fetch.html