Reduce size of llvm cache by not build webassembly target for llvm<19

[mcbarton]

@vgvassilev Due to the work to get the wasm version of xeus-cpp working we will have a wasm version of CppInterOp we will be able to test, and keep on top of from version 19. Although it will build, I suspect our wasm version of CppInterOp for llvm<19 won't work. Therefore I suggest we don't build the web assembly target for llvm<19, and remove the wasm jobs for llvm<19 so that ci runs are quicker. I've cleared the cache for 2 jobs before putting the PR in so that we can test if my changes work. If you're happy with the changes in this PR the cache will need to be cleared before merging. With the space saved in the cache by this change should give us the room in the cache for when llvm 20 is released.

[vgvassilev]

LGTM!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.55%. Comparing base (5ac8e62) to head (75f8591).
Report is 1 commits behind head on main.

Additional details and impacted files

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  Coverage   74.55%   74.55%           
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  Files           8        8           
  Lines        3211     3211           
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  Hits         2394     2394           
  Misses        817      817           

[anutosh491]

Due to the work to get the wasm version of xeus-cpp working we will have a wasm version of CppInterOp we will be able to test, and keep on top of from version 19. Although it will build, I suspect our wasm version of CppInterOp for llvm<19 won't work. Therefore I suggest we don't build the web assembly target for llvm<19, and remove the wasm jobs for llvm<19 so that ci runs are quicker.

Hey @mcbarton
I think I know on how to get a proper wasm build for CppInterOp that can be put to use for downstream projects like xeus-cpp (have been playing around locally) . It should also rid of the numerous undefined symbols out of clang as raised here (#334) .

For that I would possibly like

1. llvm 19.1.5 to be out (and the PR getting clang-repl to work in the browser to be a part of it [clang-repl] Fix generation of wasm binaries while running clang-repl in browser llvm/llvm-project#117978)
2. CppInterOp to be based on this llvm version.
3. Then I could raise a PR introducing a useable wasm build.

Maybe we could raise an issue to "fix the wasm build" (and possibly assign it to me) till then ?