[msandr] Add debugging instructions to README.txt.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@190680 91177308-0d34-0410-b5e6-96231b3b80d8
[msan] Intercept tzset.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@190682 91177308-0d34-0410-b5e6-96231b3b80d8