Migrate workflows from deprecated set-output commands

GitHub Actions provides the capability for workflow authors to use the capabilities of the GitHub Actions ToolKit
package directly in the `run` keys of workflows via "workflow commands". One such command is `set-output`, which allows
data to be passed out of a workflow step as an output.

It has been determined that this command has potential to be a security risk in some applications. For this reason,
GitHub has deprecated the command and a warning of this is shown in the workflow run summary page of any workflow using
it:

The `set-output` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more
information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

The identical capability is now provided in a safer form via the GitHub Actions "environment files" system. Migrating
the use of the deprecated workflow commands to use the `GITHUB_OUTPUT` environment file instead fixes any potential
vulnerabilities in the workflows, resolves the warnings, and avoids the eventual complete breakage of the workflows that
would result from GitHub's planned removal of the `set-output` workflow command 2023-05-31.

Author: per1234

.github/workflows/build.yml

@@ -183,7 +183,7 @@ jobs:
           OUTPUT_SAFE_BODY="${BODY//'%'/'%25'}"
           OUTPUT_SAFE_BODY="${OUTPUT_SAFE_BODY//$'\n'/'%0A'}"
           OUTPUT_SAFE_BODY="${OUTPUT_SAFE_BODY//$'\r'/'%0D'}"
-          echo "::set-output name=BODY::$OUTPUT_SAFE_BODY"
+          echo "BODY=$OUTPUT_SAFE_BODY" >> $GITHUB_OUTPUT
           echo "$BODY" > CHANGELOG.txt
 
       - name: Upload Changelog [GitHub Actions]
@@ -228,7 +228,7 @@ jobs:
       - name: Get Tag
         id: tag_name
         run: |
-          echo ::set-output name=TAG_NAME::${GITHUB_REF#refs/tags/}
+          echo "TAG_NAME=${GITHUB_REF#refs/tags/}" >> $GITHUB_OUTPUT
 
       - name: Publish Release [GitHub]
         uses: svenstaro/[email protected]

.github/workflows/check-certificates.yml

@@ -108,7 +108,7 @@ jobs:
           echo "Certificate expiration date: $EXPIRATION_DATE"
           echo "Days remaining before expiration: $DAYS_BEFORE_EXPIRATION"
 
-          echo "::set-output name=days::$DAYS_BEFORE_EXPIRATION"
+          echo "days=$DAYS_BEFORE_EXPIRATION" >> $GITHUB_OUTPUT
 
       - name: Check if expiration notification period has been reached
         id: check-expiration

.github/workflows/compose-full-changelog.yml

@@ -27,7 +27,7 @@ jobs:
       - name: Get Tag
         id: tag_name
         run: |
-          echo ::set-output name=TAG_NAME::${GITHUB_REF#refs/tags/}
+          echo "TAG_NAME=${GITHUB_REF#refs/tags/}" >> $GITHUB_OUTPUT
 
       - name: Create full changelog
         id: full-changelog

.github/workflows/sync-labels.yml

@@ -103,7 +103,7 @@ jobs:
         run: |
           # Use of this flag in the github-label-sync command will cause it to only check the validity of the
           # configuration.
-          echo "::set-output name=flag::--dry-run"
+          echo "flag=--dry-run" >> $GITHUB_OUTPUT
 
       - name: Checkout repository
         uses: actions/checkout@v3