tailscale: build with less features

Omit usually unused features:

- ipn.StateStore implementation using AWS SSM
- BIRD Internet Routing Daemon client
- tstun TAP device for bridging
- Kubernetes kubectl configuration utility
- Command line completion script generation

This shaves off about 500kb from the final executable.

net/tailscale/Makefile

@@ -28,7 +28,7 @@ GO_PKG:=\
 	tailscale.com/cmd/tailscaled
 GO_PKG_LDFLAGS:=-X 'tailscale.com/version.longStamp=$(PKG_VERSION)-$(PKG_RELEASE) (OpenWrt)'
 GO_PKG_LDFLAGS_X:=tailscale.com/version.shortStamp=$(PKG_VERSION)
-GO_PKG_TAGS:=ts_include_cli
+GO_PKG_TAGS:=ts_include_cli,ts_omit_aws,ts_omit_bird,ts_omit_tap,ts_omit_kube,ts_omit_completion
 
 include $(INCLUDE_DIR)/package.mk
 include ../../lang/golang/golang-package.mk