[asan] Fix deadlock in stack unwinder on android/x86.

Fixes PR17116.
Patch by 林作健 (manjian2006 at gmail.com).


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@190590 91177308-0d34-0410-b5e6-96231b3b80d8
[asan] hopefully make the FakeStack async-signal safe, enable the related test

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@190592 91177308-0d34-0410-b5e6-96231b3b80d8
[asan] don't lazy-init fake_stack if we only need to check that fake_stack exists (should fix 32-bit builds)

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@190593 91177308-0d34-0410-b5e6-96231b3b80d8
[asan] (part 2) don't lazy-init fake_stack if we only need to check that fake_stack exists (should fix 32-bit builds)

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@190594 91177308-0d34-0410-b5e6-96231b3b80d8