[clang-tools-extra] [clangd] Let DefineOutline tweak create a definition from scratch (PR #71950)

[Tom Praschan via cfe-commits]

tom-anders wrote:

> The new patch set properly considers "external" definitions (using the frowned-upon index lookup).

I've been using this patch for a few weeks now, and it works very well. Haven't encountered any issues/crashes yet. Performance also seems reasonable (working in a medium-sized project)

https://github.com/llvm/llvm-project/pull/71950