[asan] asan_allocator2: fix the memalign handling (clear the first word of allocated chunk in case there is an old memalign magic)

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@172603 91177308-0d34-0410-b5e6-96231b3b80d8
asan: fix ARM build


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@172613 91177308-0d34-0410-b5e6-96231b3b80d8