github: add basic CI tests

Author: kaniini

.github/workflows/test.yml

@@ -0,0 +1,59 @@
+name: Build and test libucontext
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - arch: x86
+            platform: linux/386
+            image: alpine:latest
+          - arch: x86_64
+            platform: linux/amd64
+            image: alpine:latest
+          - arch: ppc64le
+            platform: linux/ppc64le
+            image: alpine:latest
+          - arch: arm
+            platform: linux/arm/v7
+            image: alpine:latest
+          - arch: aarch64
+            platform: linux/arm64
+            image: alpine:latest
+          - arch: riscv64
+            platform: linux/riscv64
+            image: alpine:latest
+          - arch: s390x
+            platform: linux/s390x
+            image: alpine:latest
+          # Blocked by https://github.com/tonistiigi/binfmt/issues/133
+          # - arch: loongarch64
+          #   platform: linux/loong64
+          #   image: registry.alpinelinux.org/alpine:latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Set up QEMU user emulation
+        uses: docker/setup-qemu-action@v3
+        with:
+          platforms: all
+
+      - name: Build and run tests using Docker
+        run: |
+          docker run --rm \
+            --platform=${{matrix.platform}} \
+            -v "$PWD:/work" \
+            -w /work \
+            ${{matrix.image}} \
+            sh -lc '
+              apk add build-base
+              make check ARCH=${{matrix.arch}}
+            '