Adding mattermost-govet to the pipeline (#13257)

* Adding mattermost-govet to the pipeline

* Trying to fix circleCI config

* Trying to fix circleCI config

* Trying to fix circleCI config

* Trying to fix circleCI config

* Update Makefile

Co-Authored-By: Ben Schumacher <ben.schumacher@mattermost.com>

* Update Makefile

Co-Authored-By: Ben Schumacher <ben.schumacher@mattermost.com>

* Addressing PR review comments

* Addressing PR review comments

* Addressing PR review comments

* Addressing PR review comments

* Addressing PR review comments

* Addressing PR review comments

* Adding legacy check-licenses task to legacy.mk

* Removing unnecesary GO111MODULE=off lines

* Adding jenkins mattermost-govet installation

scripts/license-check.sh

@@ -1,28 +0,0 @@
-#!/usr/bin/env bash
-set -e
-IFS=$'\n'
-count=0
-for fileType in GoFiles; do
-    for file in `go list -mod=vendor -f $'{{range .GoFiles}}{{$.Dir}}/{{.}}\n{{end}}' "$@"`; do
-        case $file in
-            */utils/lru.go|*/utils/imgutils/gif.go|*/store/storetest/mocks/*|*/services/*/mocks/*|*/app/plugin/jira/plugin_*|*/plugin/plugintest/*|*/app/plugin/zoom/plugin_*|*/einterfaces/mocks/*)
-            # Third-party, doesn't require a header.
-            ;;
-        *)
-            if ! grep 'Mattermost, Inc. All Rights Reserved.' $file -q; then
-                >&2 echo "FAIL: $file is missing a license header."
-                ((count++))
-            fi
-        esac
-    done
-done
-if [ $count -eq 0 ]; then
-    exit 0
-fi
-
-if [ $count -gt 1 ]; then
-    >&2 echo "$count files are missing license headers."
-else
-    >&2 echo "$count file is missing a license header."
-fi
-exit 1