message: [CMake] Avoid libcxxabi dependency when building LLDB from the monorepo on macOS
  libc++abi became mandatory to link the libc++ binaries. LLDB only needs the build artifacts and not the linked output (we don't ship `libc++.dylib` and/or `libc++.a`). Disable the respective link steps to avoid the dependency to libc++abi.
  <rdar://problem/51980716>
diff: @@ -6,6 +6,9 @@ set(LLVM_INSTALL_TOOLCHAIN_ONLY ON CACHE BOOL "")
  set(LLVM_ENABLE_ASSERTIONS ON CACHE BOOL "")
  set(LLVM_ENABLE_MODULES ON CACHE BOOL "")
  +set(LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
  +set(LIBCXX_ENABLE_STATIC OFF CACHE BOOL "")
  +
  # Release builds set these explicitly:
  #set(LLDB_VERSION_MAJOR 9999 CACHE STRING "")
  #set(LLDB_VERSION_MINOR 9 CACHE STRING "")
  