Add 3.x workflow to master.

.github/workflows/merge_build_3x.yml

@@ -0,0 +1,35 @@
+name: Homestore 3.x Build
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - stable/v3.x
+
+jobs:
+  Build:
+    strategy:
+      fail-fast: false
+      matrix:
+        platform: ["ubuntu-22.04", "ubuntu-20.04"]
+        build-type: ["Debug", "Release"]
+        malloc-impl: ["libc", "tcmalloc"]
+        prerelease: ["True", "False"]
+        exclude:
+          - build-type: Debug
+            platform: ubuntu-20.04
+          - build-type: Debug
+            malloc-impl: tcmalloc
+          - malloc-impl: tcmalloc
+            platform: ubuntu-20.04
+          - malloc-impl: libc
+            build-type: Release
+            platform: ubuntu-22.04
+          - prerelease: "True"
+            platform: ubuntu-20.04
+    uses: ./.github/workflows/build_commit.yml
+    with:
+      platform: ${{ matrix.platform }}
+      build-type: ${{ matrix.build-type }}
+      malloc-impl: ${{ matrix.malloc-impl }}
+      prerelease: ${{ matrix.prerelease }}