[lsan] Set current_thread_tid correctly for main thread.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@184189 91177308-0d34-0410-b5e6-96231b3b80d8
[asan] fix a rare failure in fast unwinder, found by asan/clang bootstrap

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@184190 91177308-0d34-0410-b5e6-96231b3b80d8