This removes AWS and Kubernetes support from Linux binaries by default
on GOARCH values where people don't typically run on AWS or use
Kubernetes, such as 32-bit mips CPUs.
It primarily focuses on optimizing for the static binaries we
distribute. But for people building it themselves, they can set
ts_kube or ts_aws (the opposite of ts_omit_kube or ts_omit_aws) to
force it back on.
Makes tailscaled binary ~2.3MB (~7%) smaller.
Updates #7272, #10627 etc
Change-Id: I42a8775119ce006fa321462cb2d28bc985d1c146
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>