Generate coredump for linux-arm64 in debug mode.

[well-mannered-goat]

librz/debug/p/native/linux/linux_coredump.c is used to generate coredump for linux systems.

The pre defined compiler macro used for arm64 macro is __arm64__ which is incorrect, it should be __aarch64__. Check out the macros here : https://sourceforge.net/p/predef/wiki/Architectures/

Also since linux-arm64 systems dont support older ptrace request types, the code should be refactored accordingly for it.