Backport of NET-5371 License checker pt2 into release/1.16.x (#18495)

* backport of commit e0bdca41f6

* backport of commit bb76a45e5a

---------

Co-authored-by: Nathan Coleman <nathan.coleman@hashicorp.com>

.github/scripts/license_checker.sh

@@ -3,7 +3,7 @@
 # SPDX-License-Identifier: BUSL-1.1
 
 
-busl_files=$(grep -r 'SPDX-License-Identifier: BUSL' --exclude=./.github/scripts/license_checker.sh .)
+busl_files=$(grep -r 'SPDX-License-Identifier: BUSL' . --exclude-dir .github)
 
 # If we do not find a file in .changelog/, we fail the check
 if [ -n "$busl_files" ]; then

.github/workflows/license-checker.yml

@@ -7,7 +7,7 @@ name: License Checker
 
 on:
   pull_request:
-    types: [opened]
+    types: [opened, synchronize]
     branches:
       - release/1.14.*
       - release/1.15.*