Undo change to triple behavior from r199510.

The Linux distribution will be added to the ArchSpec class in an
upcoming change. This change only undoes the change to the triple. The
distribution retrieval logic and enabling of lldb-gdbserver for linux
x86_64 builds is still in place.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@199520 91177308-0d34-0410-b5e6-96231b3b80d8