Bugzilla

Nope, my previous assessment was completely wrong, there was something strange on my machine that wasn't doing what I expected.

Here's the real reason: llvm-config _does_ give us `std:c++14` on Windows, which makes our command lines look like:
`-Xclang -std=c++17 ... -std:c++14`
and I guess those end up going to two different places in clang, because it thinks c++17 is still the winner.

If we change general flag to `-std:c++17` then the override happens correctly.

Nope, my previous assessment was completely wrong, there was something strange on my machine that wasn't doing what I expected.

Here's the real reason: llvm-config _does_ give us `-std:c++14` on Windows, which makes our command lines look like:
`-Xclang -std=c++17 ... -std:c++14`
and I guess those end up going to two different places in clang, because it thinks c++17 is still the winner.

If we change our general flag to `-std:c++17` then the override happens correctly.