github: add basic CI tests

Author: kaniini

.github/workflows/test.yml

@@ -0,0 +1,58 @@
+name: Build and test libucontext
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  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: armv7
+          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}}
+          '