[windows] Don't inline fieldFromInstruction on Windows

Summary:
The VS compiler (on Windows) has a bug which results in fieldFromInstruction being optimized out in some circumstances. This only happens in *release no debug info* builds that have assertions *turned off* - in all other situations the function is not inlined, so the functionality is correct. All of the bots have assertions turned on, so this path is not regularly tested. The workaround is to not inline the function on Windows - if the bug is fixed in a later release of the VS compiler, the noinline specification can be removed.

The test that consistently reproduces this is Lanai v11.txt test.

Reviewers: asmith, labath, zturner

Subscribers: dblaikie, stella.stamenova, aprantl, JDevlieghere, llvm-commits

Differential Revision: https://reviews.llvm.org/D49753

llvm-svn: 337942