Fix build of aesni on msvc

[enginelesscc]

This fixes building LTC_AES_NI on msvc, keeps compat with clang-cl

Checklist

• ran tests (locally)

[enginelesscc]

I see no [intended] path where I could extend the CI to run with LTC_AES_NI enabled.
What do we do there?
- enable aesni by default on msvc's makefile?
- or hardcode the flag in the appveyor.yml?

[sjaeckel]

I see no [intended] path where I could extend the CI to run with LTC_AES_NI enabled.
What do we do there?

• enable aesni by default on msvc's makefile?
• or hardcode the flag in the appveyor.yml?

I see two options

• having another build&test step in the appveyor with AESNI enabled
• adding github actions on Windows support which also provides MSVC IIUC

I guess the first one would be the easiest!?