Add support for aarch64 Windows

[ilg-ul]

The initial request from @giladgd was in xpack-dev-tools/cmake-xpack#6.

[ilg-ul]

I did a first attempt to compile aarch64-w64-mingw-gcc, required to build Windows binaries, but the script failed during configure, with *** Configuration aarch64-w64-mingw-gcc not supported.

It looks like GCC 14 is not yet ready for this. I'll try again when GCC 15 is out.

[ilg-ul]

I did a second attempt to compile aarch64-w64-mingw-gcc with GCC 15, and the build failed again. I don't have time now to further investigate, and anyway I don't have a Windows arm64 machine to test the result, so we'll postpone this new feature again.

[ilg-ul]

I further investigated, and I installed wine on the latest Raspberry Pi OS, but when I tried to run an arm64 exe, it failed with:

wine: wineserver doesn't support the 01c4 architecture

The binary was compiled with llvm-mingw/aarch64-w64-mingw32uwp-gcc and is probably ok, I don't have a real Windows machine to test it:

hello-arm64.exe: PE32+ executable for MS Windows 6.00 (console), ARM64, 13 sections

In order to support aarch64 windows, a cross compiler running on Linux is necessary, and a way to test the resulting binaries, also running on linux. Neither mingw-w64 nor wine seem ready for this task now.

@giladgd, I'm afraid it'll take some time for this to be possible.