deps: Add ARM64 definitions in w32-pthreads

Update w32-pthreads/context.h to include definitions for _M_ARM and
_M_ARM64 in addition to existing ARM definitions.
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f