[benchmark] Cherrypick fix for MinGW/ARM from upstream

This fixes building for Windows on ARM, with MinGW headers.
(Building for Windows on ARM with Windows SDK still is unsupported
by the benchmark library.)

Differential Revision: https://reviews.llvm.org/D52262

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@342549 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed