Run verify generated files remake in a tmp directory

We already do this in hack/verify-generated-files.sh so we should do it
in verify-generated-files-remake.sh as well.

The idea is that any local changes made because of code generation
should not persist beyond the current run of the script.

Change-Id: I7af176773ae16c393dc2b46c006595243c9fa05b

hack/verify-generated-files-remake.sh

@@ -21,6 +21,21 @@ set -o pipefail
 KUBE_ROOT=$(dirname "${BASH_SOURCE}")/..
 source "${KUBE_ROOT}/hack/lib/init.sh"
 
+kube::util::ensure_clean_working_dir
+
+_tmpdir="$(kube::realpath $(mktemp -d -t verify-generated-files.XXXXXX))"
+kube::util::trap_add "rm -rf ${_tmpdir}" EXIT
+
+_tmp_gopath="${_tmpdir}/go"
+_tmp_kuberoot="${_tmp_gopath}/src/k8s.io/kubernetes"
+mkdir -p "${_tmp_kuberoot}/.."
+cp -a "${KUBE_ROOT}" "${_tmp_kuberoot}/.."
+
+cd "${_tmp_kuberoot}"
+
+# clean out anything from the temp dir that's not checked in
+git clean -ffxd
+
 # $1 = filename pattern as in "zz_generated.$1.go"
 function find_genfiles() {
     find .                         \