Bring back APInt self-move assignment check for MSVC only
Summary:
It was removed about a year ago in r300477. Bring it back, along with
its unittest, when the MSVC STL is in use. The MSVC STL performs
self-assignment in std::shuffle. These days, llvm::sort calls
std::shuffle when expensive checks are enabled to help find
non-determinism bugs.
Reviewers: craig.topper, chandlerc
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D46028
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@330776
91177308-0d34-0410-b5e6-
96231b3b80d8