MSVC: Use /std: instead of -std:
MSVC itself has no obvious issues with either variant but e.g. clang-tidy currently only seems to recognize the former.
Prefer it since it is also happens to be the officially documented syntax.
Option documentation is at: https://docs.microsoft.com/en-gb/cpp/build/reference/std-specify-language-standard-version
The clang-tidy version I tested with was 6.0.1.
The diagnostic it produced for the former variant is: error: unknown argument: '-std:c++17' [clang-diagnostic-error]