fix: ask clangd to not write .pch/.include cache on disk

[cmaglie]

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• [X] The PR has no duplicates (please search among the Pull Requests before creating one)
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• [ ] Tests for the changes have been added (for bug fixes / features)

What kind of change does this PR introduce? .pch files are not created on disk, but in-memory as specified with -pch-storage=memory command line flag to clangd Should finally fix #145

What is the current behavior? .pch files are created on temp directory and are not removed on exit.

What is the new behavior? .pch files are no more created on temp directory.

[cmaglie]

I understand now, thanks.

So the question now: Is there some other benefit to the proposed change?

No, there is no more reason to keep this change.