Fix "last accessed time" test failing on Windows

Before this patch, the tests in llvm/test/tools/llvm-objcopy/ELF/strip-preserve-atime.test used to fail on my machine, because the "last accessed time" is disabled in the OS by default since Windows XP. One needs to explicitly enable it for the feature to work. Otherwise the last access time is the last write time. Please see: https://superuser.com/questions/251263/the-last-access-date-is-not-changed-even-after-reading-the-file-on-windows-7

    Differential Revision: https://reviews.llvm.org/D85669