Make page size dynamic in libkvm for arm64

[andrew]

Summary

To allow for a future 16k or 64k page size we need to tell libkvm which
is being used. Add a flag field in unused space in minidumphdr and use
it to signal between the different options.

Test Plan

Kua tests pass & w -M <core> works

[markj]

lib/libkvm/kvm_minidump_aarch64.c

51

The line break doesn't seem to be needed.

108

Is it supposed to be vmst->hdr.version < 1?

188–190

Maybe define aarch64_trunc_page() to complement aarch64_round_page().

[andrew]

• Remove a line break
• Fix version check
• Add aarch64_trunc_page