make : update MSYS_NT (#1813)

make : update MSYS_NT (#1813)

I just upgraded the R wrapper at https://github.com/bnosac/audio.whisper to use whisper.cpp 1.5.4
I'm working on Windows and noticed while doing that that it did not pick up the relevant CFLAGS/CXXFLAGS as my system showed

```
I whisper.cpp build info:
I UNAME_S:  MSYS_NT-10.0-19045
I UNAME_P:  unknown
I UNAME_M:  x86_64
```

Many thanks for all the tremendous hard work on maintaining whisper.cpp!