Setting GOBIN was not sufficient, something deeper in
the build process is invoking the go tool without $GOBIN.
Instead, require it be first in $PATH.
This is necessary to fix
https://github.com/tailscale/tailscale/issues/2450
and (hopefully)
https://github.com/tailscale/tailscale/issues/2478
which are a SECCOMP crash in accept() which we have
patched in the Tailscale toolchain by pulling in
an early patch from go 1.17.
Signed-off-by: Denton Gentry <dgentry@tailscale.com>