Zig with version 0.9.1 changed behaviour when missing Mac OSX Frameworks from warning to error as explained here
This PR adds automatic SDK installation on Linux, while on Windows it expects for SDK to be preinstalled and path to it provided with --sdk flag. SDK has a lot of symlinks and any possible solution that I tried on Windows, packing it with zip or with tar using --dereference, didn't worked. Using any combination of zip, 7z, tar, zippy.ziparchives.extractAll() and zippy.tarballs.extractAll()` failed.

Probably due what is explained in clang 15 Release notes

The -Wint-conversion warning diagnostic for implicit int <-> pointer conversions now defaults to an error in all C language modes. It may be downgraded to a warning with -Wno-error=int-conversion, or disabled entirely with -Wno-int-conversion.

Now threading test from windows|macosx to linux-amd64 fails with following error:

error: incompatible integer to pointer conversion passing 'unsigned long' to parameter of type 'pthread_t' (aka 'struct __pthread *') [-Wint-conversion]
        T1_ = pthread_join(t.sys, ((void**) NIM_NIL));
                           ^~~~~

Passing -Wno-error=int-conversion reverts its to a warning.

All Mac OSX SDKs can be found here and download should be cleaned (keep only MacOSX stuff) and hosted somewhere, maybe as a repo's release artifact.

All tests passed in my fork - https://github.com/vandot/nimxc/actions/runs/4590217179