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

[Jonas Devlieghere via cfe-commits]

JDevlieghere wrote:

> 1. Windows support

Windows support is definitely lacking which probably means a bunch of tests don't run there. We do have [one buildbot](https://lab.llvm.org/buildbot/#/builders/219) that runs on Windows so I have a hard time believing it's totally broken. The last runs are consistently green and based on the number of tests it seems to still cover a remarkable subset of the test suite. 

> 2. Build system does not support Multi-config generators. You can grep for https://cmake.org/cmake/help/latest/variable/CMAKE_CFG_INTDIR.html as an example.

This simply isn't true. Xcode is a multi-config build system and we have [a bot](https://ci.swift.org/view/all/job/llvm.org/view/LLDB/job/lldb-cmake-standalone/) that ensures that doesn't break. Maybe there's something different about MSVC? 

> 3. Not all tests pass and it's quite unclear when that is not your fault.

I really sympathize with this one. Most of that's boils down to how much we have to rely on the OS and other tools (the compiler, the linker, etc) for our integration tests. Having more tests written as unit tests or regression tests using `lldb-test` will help with that. I think we (the lldb community) can be more vigilant on that front in pushing for those tests. 👍

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