[clang] [libc++] Add a CI job for the LLDB data formatters (PR #65174)

[Michael Buch via cfe-commits]

================
@@ -574,6 +574,20 @@ benchmarks)
     generate-cmake
     check-cxx-benchmarks
 ;;
+check-lldb-data-formatters)
+    clean
+    ${CMAKE}                                        \
+        -S "${MONOREPO_ROOT}/llvm"                  \
+        -B "${BUILD_DIR}"                           \
+        -GNinja -DCMAKE_MAKE_PROGRAM="${NINJA}"     \
+        -DCMAKE_BUILD_TYPE=RelWithDebInfo           \
+        -DLLVM_ENABLE_ASSERTIONS=ON                 \
+        -DLLDB_ENABLE_PYTHON=ON                     \
+        -DLLVM_ENABLE_PROJECTS='llvm;clang;lldb'    \
+        -DLLVM_ENABLE_RUNTIMES='libcxx;libcxxabi'
+
+    ${NINJA} -C "${BUILD_DIR}" check-lldb-api-functionalities-data-formatter-data-formatter-stl-libcxx
----------------
Michael137 wrote:

I think using a "standalone" build of LLDB would make sense here? Correct me if I'm wrong @adrian-prantl @JDevlieghere 
Here is how we configure it for the [standalone bot](https://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake-standalone/): https://github.com/llvm/llvm-project/pull/65174#discussion_r1357566522

So if we have a clang build already, we can just point the LLDB build to those artifacts as follows:
```
                 '-DLLVM_DIR={}'.format(llvm_dir),
                 '-DClang_DIR={}'.format(clang_dir),
```

https://github.com/llvm/llvm-project/pull/65174