[docs] Mention that dwarf unwinding should be supported on arm64/windows

This didn't require any further changes to libunwind as long as win64
in general is handled correctly.

Differential Revision: https://reviews.llvm.org/D39632

git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@318383 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed