Add one-off gcc release version build workflow

For Ubuntu 24.04 migration: rebuild old gcc versions (5.x-11.x) with
modern binutils (2.44) after removing the old version pins in gcc-builder.

Usage:
  gh workflow run build-gcc-release.yml -R compiler-explorer/compiler-workflows -f version=5.5.0

🤖 Generated by LLM (Claude, via OpenClaw)

Author: mattgodbolt-molty

.github/workflows/build-gcc-release.yml

@@ -0,0 +1,27 @@
+name: Build gcc release version
+run-name: Build gcc ${{ inputs.version }}
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'GCC version to build (e.g. 5.5.0, 8.5.0)'
+        required: true
+        type: string
+
+jobs:
+  build:
+    runs-on: [ 'self-hosted', 'ce', 'linux', 'x64' ]
+    steps:
+      - name: Start from a clean directory
+        uses: AutoModality/action-clean@v1.1.0
+      - uses: actions/checkout@v4
+      - name: Run the build
+        uses: ./.github/actions/daily-build
+        with:
+          image: gcc
+          name: gcc-${{ inputs.version }}
+          command: build.sh
+          args: ${{ inputs.version }}
+          AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
+          AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}