boot-fake-node: use uname -m instead of -p

[nick1udwig]

Problem

Resolves #49

Solution

Here and in Kinode core (hyperware-ai/hyperdrive#253) replace uname -p with uname -m.

Docs Update

N/A

Notes

Will require some amount of backwards compatibility for Mac x86_64 / i386 since some users may use an older kit that uses -p and others may use this version that uses -m.