Also add build files for deps DebugInfo/Symbolize, ToolDrivers/dll-tool.
Also add gn/build/libs/xar (needed by llvm-objdump).
Also delete an incorrect part of the symlink description in //BUILD.gn (it used
to be true before I made the symlink step write a stamp file; now it's no
longer true).
These are all binaries needed by check-lld that need symlinks.
Differential Revision: https://reviews.llvm.org/D55743
llvm-svn: 349486
Nico Weber