updates tailscale/tailscale#13476
On darwin, os.Hostname is no longer reliable when called
from a sandboxed process. To fix this, we will allow clients
to set an optional callback to query the hostname via an
alternative native API.
We will leave the default implementation as os.Hostname since
this works perfectly well for almost everything besides sandboxed
darwin clients.
Signed-off-by: Jonathan Nobels <jonathan@tailscale.com>
This updates all source files to use a new standard header for copyright
and license declaration. Notably, copyright no longer includes a date,
and we now use the standard SPDX-License-Identifier header.
This commit was done almost entirely mechanically with perl, and then
some minimal manual fixes.
Updates #6865
Signed-off-by: Will Norris <will@tailscale.com>
