Optimized release for x86-64 v4 architecture

Would it be useful to have an optimized release for the most recent CPUs? In particular the **x86-64 v4** architecture supported by GCC via compiler flag `-march=x86-64-v4`. Or **x86-64 v3** architecture is supported by GCC via compiler flag `-march=x86-64-v3`, which may support a wider viriety of recent CPUs. See [this link](https://en.wikipedia.org/wiki/X86-64#Microarchitecture_levels) for a list of which CPUs are included in these microarchitecture levels. But as this could trigger issue #285 it would be best to disable AVX instructions using compiler flag `-mno-avx`. Basically this would optimize for the 2017 Intel Skylake-X architecture, excluding Intel-specific instructions so AMD Zen4 or newer processors are also supported. A release built with these compiler flags has been published [here (x86-64 v4)](https://github.com/brechtsanders/winlibs_mingw/releases/tag/15.2.0posix-13.0.0-msvcrt-r1-x86-64-v4) and [here (x86-64 v3)](https://github.com/brechtsanders/winlibs_mingw/releases/tag/15.2.0mcf-13.0.0-ucrt-r1-x86-64-v3).