Enable LLDB tests in Linux pre-merge CI (#94208)

This patch removes LLDB from a list of projects that are excluded from
building and testing on pre-merge CI on Linux.

Windows environment needs to be prepared in order to test LLDB
(https://github.com/llvm/llvm-project/pull/94208#issuecomment-2146256857),
but we don't have enough maintenance resources to do that at the moment.

Because LLDB has been in the list of projects that need to be tested on
Clang changes, this PR make this happen on Linux. This seems to be the
consensus in the discussion of this PR.