Add LTO environment variable storage step

.github/workflows/build.yml

@@ -69,6 +69,9 @@ jobs:
       - name: Store branch as env variable
         run: BRANCH=${{ inputs.branch }} && echo "BRANCH=$BRANCH" >> $GITHUB_ENV
 
+      - name: Store LTO as env variable
+        run: LTO=${{ inputs.lto }} && echo "LTO=$LTO" >> $GITHUB_ENV
+
       - name: get kernel version before cloning
         uses: ./.github/actions/kernel-info