Visual Studio 2019 includes ARM64 cross-compiler.
While our CI is not capable of running any tests on it, we can clean up code to remove the
hardcoded assumption that Windows equates Intel, perhaps such a cleanup could be useful in the future, when AMD64 ecosystem evolves

The cross-compilation works like this

patch wolfssl

Fix wolfssl - apply that patch
https://github.com/vaintroub/wolfssl/commit/29968716ea050fd905be55cec7e290a674fd075d

Hopefully it will be fixed soon in wolfssl proper.

build tools used during cross-compilation - comp_err, gen_lex_hash

cd sourcedir

mkdir x64

cd x64

cmake ..

cmake --build . --target import_executables --config relwithdebinfo

build ARM64, crosscompilation

cd sourcedir

mkdir arm64

cd arm64

cmake .. -A ARM64 -DCMAKE_SYSTEM_NAME=Windows -DIMPORT_EXECUTABLES=C:/path/to/sourcedir/x64/import_executables.cmake

cmake --build . --config relwithdebinfo

# packaging, as usual

cmake --build . --config relwithdebinfo --target win_package

cmake --build . --config relwithdebinfo --target MSI

Note , that setting -DCMAKE_SYSTEM_NAME is how CMake known that we're crosscompiling
-DIMPORT_EXECUTABLES=C:/path/to/sourcedir/x64/import_executables.cmake lets the native (x64) auxiliary executables run during build process, and -A ARM64 is CMake-ish way to chose the ARM64 cross-compiler.

To build MSI, WIX toolset version 3.14 is necessary, which is still under development, but betas are available. No other WIX version can handle ARM64 yet.