Add natlabapp.arm64 config and gokrazydeps.go for building a gokrazy
natlab appliance image targeting arm64 (Apple Silicon). This is the
arm64 counterpart to the existing natlabapp (amd64) used by vmtest.
The arm64 image uses github.com/gokrazy/kernel.arm64 and is built
with "make natlab-arm64" in the gokrazy directory.
Updates #13038
Change-Id: I0e1f8e5840083a5de5954f2cf46e3babec129d96
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Brad Fitzpatrick