[ASan] Make sure slow stack unwinder doesn't return empty stacks.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@194107 91177308-0d34-0410-b5e6-96231b3b80d8
[ASan] Disable back init-order checker. Make strict_init_order imply check_initialization_order

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@194125 91177308-0d34-0410-b5e6-96231b3b80d8