[CMake] add_lld_library: link_system_libs is not needed any more. LLVMSupport may provide dependencies to system libs.
[CMake] add_lld_library: link_system_libs is not needed any more. LLVMSupport may provide dependencies to system libs.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@201967 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld