Add test/typecheck, a fast typecheck for all build platforms.

Most of the time spent compiling is spent optimizing and linking
binary code. Most errors occur at the syntax or semantic (type) layers.
Go's compiler is importable as a normal package, so we can do fast
syntax and type checking for the 10 platforms we build on.

This currently takes ~6 minutes of CPU time (parallelized).

This makes presubmit cross builds superfluous, since it should catch
most cross-build breaks (generally Unix and 64-bit assumptions).

Example output:

$ time go run test/typecheck/main.go
type-checking:  linux/amd64, windows/386, darwin/amd64, linux/arm, linux/386, windows/amd64, linux/arm64, linux/ppc64le, linux/s390x, darwin/386
ERROR(windows/amd64) pkg/proxy/ipvs/proxier.go:1708:27: ENXIO not declared by package unix
ERROR(windows/386) pkg/proxy/ipvs/proxier.go:1708:27: ENXIO not declared by package unix

real	0m45.083s
user	6m15.504s
sys	1m14.000s

hack/make-rules/verify.sh

@@ -30,6 +30,7 @@ EXCLUDED_PATTERNS=(
   "verify-linkcheck.sh"          # runs in separate Jenkins job once per day due to high network usage
   "verify-test-owners.sh"        # TODO(rmmh): figure out how to avoid endless conflicts
   "verify-*-dockerized.sh"       # Don't run any scripts that intended to be run dockerized
+  "verify-typecheck.sh"          # runs in separate typecheck job
   )
 
 # Only run whitelisted fast checks in quick mode.

hack/verify-typecheck.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+
+# Copyright 2018 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+KUBE_ROOT=$(dirname "${BASH_SOURCE}")/..
+source "${KUBE_ROOT}/hack/lib/init.sh"
+
+kube::golang::verify_go_version
+
+cd "${KUBE_ROOT}"
+
+ret=0
+go run test/typecheck/main.go "$@" || ret=$?
+if [[ $ret -ne 0 ]]; then
+  echo "!!! Type Check has failed. This may cause cross platform build failures." >&2
+  echo "!!! Please see https://git.k8s.io/kubernetes/test/typecheck for more information." >&2
+  exit 1
+fi