[CMake] macOS: Find DebugSymbols.framework inside the SDK

[jordan_rose]

Summary

It's always going to be at / on disk, but that's not what we should be linking against! This won't actually change anything in practice, but it's "more correct", and may be necessary if Apple ever decides to move the implementation of DebugSymbols.framework to another library.

[davide]

LGTM

[sgraenitz]

LGTM too. Did this land?

lldb/cmake/modules/LLDBConfig.cmake

if (NOT LIBXML2_FOUND)
   find_package(LibXml2)
 endif()
 
 # Find libraries or frameworks that may be needed
 if (APPLE)
   if(NOT IOS)
     find_library(CARBON_LIBRARY Carbon)
     find_library(CORE_SERVICES_LIBRARY CoreServices)
-    find_library(DEBUG_SYMBOLS_LIBRARY DebugSymbols PATHS "/System/Library/PrivateFrameworks")
+    find_library(DEBUG_SYMBOLS_LIBRARY DebugSymbols PATHS "${CMAKE_OSX_SYSROOT}/System/Library/PrivateFrameworks")
   endif()
   find_library(FOUNDATION_LIBRARY Foundation)
   find_library(CORE_FOUNDATION_LIBRARY CoreFoundation)
   find_library(SECURITY_LIBRARY Security)
 
   add_definitions( -DLIBXML2_DEFINED )
   list(APPEND system_libs xml2
        ${CURSES_LIBRARIES}