[CMake] Fix standalone build for debugserver on macOS

[sgraenitz]

Summary

Quick-fix to avoid CMake config issue:

CMake Error at /path/to/lldb/cmake/modules/AddLLDB.cmake:116 (add_dependencies):
  Cannot add target-level dependencies to non-existent target "lldb-suite".

[xiaobai]

This change looks fine to me. Have you considered creating something like a "debugserverStandalone.cmake" file similar to how LLDB standalone builds work? Might save us from some duplication, but I'm not sure if it would be overkill.

[sgraenitz]

Thought about it, but yes, at the moment it looks like overkill. I'd go on duplicating options to debugserver for now and change the approach if it gets unpractical. There are some more changes to come. I want to upstream these first and see how it looks then.

lldb/trunk/tools/debugserver/CMakeLists.txt

 cmake_minimum_required(VERSION 3.4.3)
 
 project(Debugserver LANGUAGES C CXX ASM-ATT)
 
 if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   set(CMAKE_MODULE_PATH
     ${CMAKE_MODULE_PATH}
     "${CMAKE_SOURCE_DIR}/../../cmake"
     "${CMAKE_SOURCE_DIR}/../../cmake/modules"
     )
-  
   include(LLDBStandalone)
   include(AddLLDB)
 
   set(LLDB_SOURCE_DIR "${CMAKE_SOURCE_DIR}/../../")
   include_directories(${LLDB_SOURCE_DIR}/include)
+
+  # lldb-suite is a dummy target that encompasses all the necessary tools and
+  # libraries for building a fully-functioning liblldb.
+  add_custom_target(lldb-suite)
+  set(LLDB_SUITE_TARGET lldb-suite)
 endif()
 
 add_subdirectory(source)