Building an existing project (json-c) for wasm

Hi,
I'm trying to build an existing library project to parse json within wasm module.
The project I've choosen is json-c https://github.com/json-c/json-c
I followed the guide adapting it for cmake projects https://emscripten.org/docs/compiling/Building-Projects.html

But when I try the command:
`$ emcmake ../cmake-configure`

I'm getting the error:
`
configure: ../cmake-configure -DCMAKE_TOOLCHAIN_FILE=/opt/Programs/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_CROSSCOMPILING_EMULATOR="/opt/Programs/emsdk/node/12.18.1_64bit/bin/node"
cmake version 3.16.3

CMake suite maintained and supported by Kitware (kitware.com/cmake).
ERROR: Unknown arguments: -DCMAKE_TOOLCHAIN_FILE=/opt/Programs/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_CROSSCOMPILING_EMULATOR="/opt/Programs/emsdk/node/12.18.1_64bit/bin/node"
../cmake-configure [] [-- []]
--prefix=PREFIX install architecture-independent files in PREFIX
--enable-threading Enable code to support partly multi-threaded use
--enable-rdrand Enable RDRAND Hardware RNG Hash Seed generation on
supported x86/x64 platforms.
--enable-shared build shared libraries [default=yes]
--enable-static build static libraries [default=yes]
--disable-Bsymbolic Avoid linking with -Bsymbolic-function
--disable-werror Avoid treating compiler warnings as fatal errors
`

I'm stuck here...
Any help would be really appreciated.
**Thanks a lot**