[llvm] [bazel] Add support for building lldb (PR #87589)

[Haojian Wu via llvm-commits]

hokein wrote:

IIUC, the `debugserver` binary and its dependencies (e.g. `DebugServerCommon`) are only available on MacOS. If we build these targets explicitly with bazel on Linux, bazel will give the `incompatible and cannot be built, but was explicitly requested.` error message.

The bazel buildkite setup is like:
1. run `bazelisk query //... + @llvm-project//...` command to list all available targets;
2. run `bazelisk test` on each target which is list in step1;

Step1 lists some incompatible targets like `DebugServerCommon` which causes the issue. I guess the fix is to not emit these incompatible targets in step1 for non-MacOS platforms. 


https://github.com/llvm/llvm-project/pull/87589