actions: add x86-legacy build workflow

.github/workflows/build-gluon.yml

@@ -412,6 +412,27 @@ jobs:
           name: x86-geode_output
           path: output
 
+  x86-legacy:
+    name: x86-legacy
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: Install Dependencies
+        run: sudo contrib/actions/install-dependencies.sh
+      - name: Build
+        run: contrib/actions/run-build.sh x86-legacy
+      - name: Archive build logs
+        if: ${{ !cancelled() }}
+        uses: actions/upload-artifact@v1
+        with:
+          name: x86-legacy_logs
+          path: openwrt/logs
+      - name: Archive build output
+        uses: actions/upload-artifact@v1
+        with:
+          name: x86-legacy_output
+          path: output
+
   x86-64:
     name: x86-64
     runs-on: ubuntu-latest