Source code is missing for arm64 build

I'm trying to make ChakraCore running on arm64 properly. Although it seems to ChakraCore doesn't support arm64 officially (at least can't build for arm64 using build script), but the codes for arm64 is almost ready in code base except for unixasmmacrosarm64.inc is used by others but doesn't exist in the project.

What is the good way to complement these missing files to ChakraCore code base? Can't build it for arm64 without unixasmmacrosarm64.inc