MSVC's pragma optimize turns optimizations on or off based on the list
passed. At the moment, we only support an empty optimization list.
i.e. `#pragma optimize("", on | off)`
From MSVC's docs:
| Parameter | Type of optimization |
|-----------|--------------------------------------------------|
| g | Enable global optimizations. Deprecated |
| s or t | Specify short or fast sequences of machine code |
| y | Generate frame pointers on the program stack |
https://docs.microsoft.com/en-us/cpp/preprocessor/optimize?view=msvc-170
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D125723
Stephen Long