Ensure LLVM_EXTERNALIZE_DEBUGINFO goes to bin/ not foo/bar/

[directhex]

Summary

This aligns with the Windows behaviour, where .pdb files go to bin/ not foo/bar/ (e.g. tools/llc/) - and it makes more sense to put the debug files next to the executables that they pair with.

If LLVM_EXTERNALIZE_DEBUGINFO_OUTPUT_DIR is absolute, put files in there, otherwise the path is relative to bin/ not foo/bar/.

llvm/cmake/modules/AddLLVM.cmake

       set(CMAKE_DSYMUTIL xcrun dsymutil)
     endif()
     add_custom_command(TARGET ${name} POST_BUILD
+      WORKING_DIRECTORY ${LLVM_RUNTIME_OUTPUT_INTDIR}
       COMMAND ${CMAKE_DSYMUTIL} ${output_path} $<TARGET_FILE:${name}>
       ${strip_command}
       )

       # If an output dir is specified, it must be manually mkdir'd on Linux,
       # as that directory needs to exist before we can pipe to a file in it.
       add_custom_command(TARGET ${name} POST_BUILD
+        WORKING_DIRECTORY ${LLVM_RUNTIME_OUTPUT_INTDIR}
         COMMAND ${CMAKE_COMMAND} -E make_directory ${LLVM_EXTERNALIZE_DEBUGINFO_OUTPUT_DIR}
         )
     else()

     endif()
 
     add_custom_command(TARGET ${name} POST_BUILD
+      WORKING_DIRECTORY ${LLVM_RUNTIME_OUTPUT_INTDIR}
       COMMAND ${CMAKE_OBJCOPY} --only-keep-debug $<TARGET_FILE:${name}> ${output_path}
       ${strip_command} -R .gnu_debuglink
       COMMAND ${CMAKE_OBJCOPY} --add-gnu-debuglink=${output_path} $<TARGET_FILE:${name}>