build portability

[belm0]

I noticed a few issues in my environment

c++17 standard is not being applied

Maybe the current config only happens to work if the C++ compiler defaults to 17?

I had to add this to top level CMakeLists.txt:

set(CMAKE_CXX_STANDARD 17)

ext/google_benchmark assumes Windows

needed to disable hard-coded lib shlwapi in ext/google_benchmark/CMakeLists.txt