Work around INPUT_* missing in composite action (JIRA BLD-5704)

See actions/runner#665

Author: siong-chin

action.yml

@@ -1,15 +1,17 @@
 name: CCDC File Checks
 author: CCDC
 description: Check changed files for compliance
+inputs:
+  commitMessage:
+    description: 'The commit message'
+    required: true
 runs:
   using: "composite"
   steps:
     - run: python3 $GITHUB_ACTION_PATH/main.py
       shell: bash
-inputs:
-  commitMessage:
-    description: 'The commit message'
-    required: true
+      env:
+        INPUT_COMMITMESSAGE: ${{ inputs.commitMessage }}
 branding:
   icon: 'check-square'
   color: 'green'