Add workflow to build binary

.github/workflows/build.yaml

@@ -0,0 +1,87 @@
+name: Build su-exec
+
+on:
+  push:
+    branches: ["**"]
+    tags:
+      - "v*"
+  pull_request:
+
+jobs:
+  build-ubuntu:
+    name: Ubuntu build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install build deps
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential
+
+      - name: Build
+        run: make
+
+      - name: Show binary info
+        run: |
+          ls -l su-exec
+          file su-exec
+
+  build-static:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - platform: linux/amd64
+            arch: amd64
+          - platform: linux/arm64
+            arch: arm64
+          - platform: linux/ppc64le
+            arch: ppc64le
+          - platform: linux/riscv64
+            arch: riscv64
+          - platform: linux/s390x
+            arch: s390x
+          - platform: linux/arm/v7
+            arch: armv7
+          - platform: linux/386
+            arch: x86
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Enable QEMU
+        uses: docker/setup-qemu-action@v3
+        with:
+          platforms: all
+
+      - name: Build static inside Alpine (${{ matrix.arch }})
+        shell: bash
+        run: |
+          set -euxo pipefail
+
+          docker run --rm \
+            --platform=${{ matrix.platform }} \
+            -e HOST_UID="$(id -u)" \
+            -e HOST_GID="$(id -g)" \
+            -v "$PWD":/src -w /src \
+            alpine:3.22 \
+            sh -exc '
+              apk add --no-cache build-base file
+              make clean
+              make su-exec
+              ./su-exec "$HOST_UID:$HOST_GID" make su-exec-static
+              ./su-exec "$HOST_UID:$HOST_GID" strip su-exec-static
+              file su-exec-static
+            '
+
+          mv su-exec-static su-exec-static-${{ matrix.arch }}
+
+      - name: Upload artifact (${{ matrix.arch }})
+        uses: actions/upload-artifact@v4
+        with:
+          name: su-exec-static-${{ matrix.arch }}
+          path: su-exec-static-${{ matrix.arch }}