Fix check-xeus-cpp command

[anutosh491]

Description

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Fixes # (issue)

Type of change

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• Bug fix
• New feature
• Added/removed dependencies
• Required documentation updates

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.77%. Comparing base (f622f5f) to head (b9258b0).

Additional details and impacted files

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  Coverage   81.77%   81.77%           
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  Files          20       20           
  Lines         845      845           
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  Hits          691      691           
  Misses        154      154           

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[anutosh491]

So two problems from my previous PR #400

1. the check_xeus_cpp executable is also responsible for the build and then the test. As we're building using emscripten, let's stick to emmake.

2. We should switch when do we install and add node to our path.

Reason

• If you check the build CI in Use node version 22 to run wasm based tests #400, we have this during the build

configure: cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/home/runner/micromamba/envs/xeus-cpp-wasm-host -DXEUS_CPP_EMSCRIPTEN_WASM_BUILD=ON -DCMAKE_FIND_ROOT_PATH=/home/runner/micromamba/envs/xeus-cpp-wasm-host -DSYSROOT_PATH=/home/runner/micromamba/envs/xeus-cpp-wasm-build/opt/emsdk/upstream/emscripten/cache/sysroot -DCMAKE_COMPILE_WARNING_AS_ERROR=ON .. -DCMAKE_TOOLCHAIN_FILE=/home/runner/micromamba/envs/xeus-cpp-wasm-build/opt/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_CROSSCOMPILING_EMULATOR=/home/runner/micromamba/envs/xeus-cpp-wasm-build/bin/node

Check the last line here : We're still using node from the xeus-cpp-wasm-build for the emulator. That's still node 16.

• The CI for this PR has

configure: cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/home/runner/micromamba/envs/xeus-cpp-wasm-host -DXEUS_CPP_EMSCRIPTEN_WASM_BUILD=ON -DCMAKE_FIND_ROOT_PATH=/home/runner/micromamba/envs/xeus-cpp-wasm-host -DSYSROOT_PATH=/home/runner/micromamba/envs/xeus-cpp-wasm-build/opt/emsdk/upstream/emscripten/cache/sysroot -DCMAKE_COMPILE_WARNING_AS_ERROR=ON .. -DCMAKE_TOOLCHAIN_FILE=/home/runner/micromamba/envs/xeus-cpp-wasm-build/opt/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_CROSSCOMPILING_EMULATOR=/home/runner/micromamba/envs/node-env/bin/node

So now we're correctly overriding the node we want to use for the emulator for building/testing.