Fix faulty CMAKE_FIND_ROOT_PATH_MODE_PACKAGE used for the wasm build

[anutosh491]

Description

I'm not sure which PR introduced CMAKE_FIND_ROOT_PATH_MODE_PACKAGE but it is being used wrongly.

Cmake docs say that there are only 3 values this variables accepts

1. ONLY
2. NEVER
3. BOTH

What we are using is something like CMAKE_FIND_ROOT_PATH_MODE_PACKAGE=ON which doesn't make sense (its wrong but somehow the build just works)

Please tick all options which are relevant.

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

[anutosh491]

As the docs say CMAKE_FIND_ROOT_PATH_MODE_PACKAGE basically controls two variables
i) CMAKE_FIND_ROOT_PATH
ii) CMAKE_SYSROOT

As far as my understanding goes we just need to control the CMAKE_FIND_ROOT_PATH that cmake uses while cross-compiling.

When cross-compiling (for example, when using Emscripten), CMake normally uses the host system's root directory as the search root. CMAKE_FIND_ROOT_PATH allows you to override this behavior and specify alternate directories that CMake should treat as the root for package discovery.

So in this case we don't even need to control both vars through CMAKE_FIND_ROOT_PATH_MODE_PACKAGE as CMAKE_SYSROOT is not really of use to us.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.72%. Comparing base (ac45e1f) to head (41ba265).

Additional details and impacted files

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  Coverage   80.72%   80.72%           
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  Files          19       19           
  Lines         970      970           
  Branches       93       93           
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  Hits          783      783           
  Misses        187      187           

[anutosh491]

cc @mcbarton for reviews

It was a faulty thing on xeus (xeus-cookiecutter) which was responsible for this. I fixed it on xeus yersterday (jupyter-xeus/xeus#416)

We need to do the same on libraries that might affect xeus-cpp (I don't think other libraries have this mistake but cppinterop does use CMAKE_FIND_ROOT_PATH_MODE_PACKAGE=ON which needs to be fixed)

[mcbarton]

@anutosh491 If removing CMAKE_PREFIX_PATH from the cmake config shouldn't you also remove where you export this variable just before building?

[anutosh491]

you also remove where you export this variable just before building?

Absolutely, that's not required for the build.