[clang] [llvm] Enable LLDB tests in Linux pre-merge CI (PR #94208)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

@Endilll This looks good, thanks!

How will this affect test capacity? Right now, the Linux bots are lagging, while the Windows bot is breezing through.

This is the opposite of the usual. Are we under-provisioned on Linux CI resources? How much worse will it get when we add this extra workload?

https://github.com/llvm/llvm-project/pull/94208