Make hack scripts use go install and assume PATH

Now that they all call setup_env, we don't need find-binary (I think).
That was originally meant to hide the diff between docker and local
builds but all these tools do local builds anyway.

hack/verify-description.sh

@@ -28,12 +28,7 @@ source "${KUBE_ROOT}/hack/lib/util.sh"
 
 kube::golang::setup_env
 
-make -C "${KUBE_ROOT}" WHAT=cmd/genswaggertypedocs
-
-# Find binary
-genswaggertypedocs=$(kube::util::find-binary "genswaggertypedocs")
-
-result=0
+GOPROXY=off go install ./cmd/genswaggertypedocs
 
 find_files() {
   find . -not \( \
@@ -69,10 +64,11 @@ kube::util::check-file-in-alphabetical-order "${failure_file}"
 failing_files=()
 while IFS='' read -r line; do failing_files+=("$line"); done < <(cat "$failure_file")
 
+result=0
 for file in $versioned_api_files; do
   if ! kube::util::array_contains "$file" "${failing_files[@]}"; then
     gen_swagger_result=0
-    $genswaggertypedocs -v -s "${file}" -f - || gen_swagger_result=$?
+    genswaggertypedocs -v -s "${file}" -f - || gen_swagger_result=$?
     if [[ "${gen_swagger_result}" -ne 0 ]]; then
       echo "API file: ${file} is missing: ${gen_swagger_result} descriptions"
       result=1