[libtorrent] fix build error on windows arm64 target

[wbsdty331]

fixes: #17320
libtorrent only focus AMD64 and i386 platform, when build for arm64 it will throw error. This pr fix it.

reference: arvidn/libtorrent#7313

If upstream merge my pr and release new version, I will delete this path from vcpkg repoistry.

[JavierMatosD]

Can you give some more details as to why this patch fixes / enables arm64 support?

[wbsdty331]

I want to build arm64 libtorrent with MSVC arm64 build toolchin and VS2022,but I got an error with assert.cpp.
let me see the original code:

#if defined(_WIN64)
	int const machine_type = IMAGE_FILE_MACHINE_AMD64;
	stack_frame.AddrPC.Offset = context_record.Rip;
	stack_frame.AddrFrame.Offset = context_record.Rbp;
	stack_frame.AddrStack.Offset = context_record.Rsp;
#else
	int const machine_type = IMAGE_FILE_MACHINE_I386;
	stack_frame.AddrPC.Offset = context_record.Eip;
	stack_frame.AddrFrame.Offset = context_record.Ebp;
	stack_frame.AddrStack.Offset = context_record.Esp;
#endif

from MSDN Predefined preprocessor macros we can know:

_WIN64 Defined as 1 when the compilation target is 64-bit ARM or x64. Otherwise, undefined.

original code only focused on i386 and x86_64 platform, but stackframe have dependencies on different CPU registers (Rip rbp Ebp and so on),

It means arm64 architectures in this define is also true. for x86_64 cpu, the code is ok, but arm64 processor don't have Rip Rbp and Rsp registers, and MACHINE_TYPE is also wrong, so you must use arm64 CPU register and MACHINE_TYPE to use stackframe.

ref: https://learn.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions?view=msvc-170

[JavierMatosD]

Thank you for the explanation! :)