Revert "Fix llvm::Optional build breaks in MSVC using std::is_trivially_copyable"

This reverts commit 854f0984.

This breaks compilation with clang-cl on Windows, while in a MSVC 16.8 cmd.exe.
This also breaks PPC: http://lab.llvm.org:8011/#/builders/93/builds/1435
And: https://reviews.llvm.org/D93510#2497737