benchmark

Audit MSVC references in cmake files to consider clang++ (#1669)

There are three major compilers on Windows targeting the MSVC ABI (i.e.
linking with microsofts STL etc.):
  - `MSVC`
  - `clang-cl` aka clang with the MSVC compatible CLI
  - `clang++` aka clang with gcc compatible CLI

The cmake variable `MSVC` is only set for the first two as it defined in
terms of the CLI interface provided:

> Set to true when the compiler is some version of Microsoft Visual
> C++ or another compiler simulating the Visual C++ cl command-line syntax.

(from cmake docs)

For many of the tests in the library its the ABI that matters not the
cmdline, so check `CMAKE_CXX_SIMULATE_ID` too, if it is `MSVC` the
current compiler is targeting the MSVC ABI. This handles `clang++`