Revert a final patch that was committed without the author contributing
it to the LLVM project through the appropriate channels.

This reverts:
r195837: "[Sanitizer] Add rudimentary support for using libbacktrace in ..."

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@196875 91177308-0d34-0410-b5e6-96231b3b80d8