Introduce CI workflow based on GitHub Actions (#114)

This introduces GitHub CI which runs builds and tests in a matrix configuration. It also changes the systemd repo to stable one. And puts the CI badge (plus a few more badges) to the README page.

Fixes #44

.github/workflows/ci.yml

@@ -0,0 +1,68 @@
+name: CI
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-18.04, ubuntu-20.04]
+        compiler: [g++, clang]
+        build: [shared-libsystemd]
+        include:
+          - os: ubuntu-20.04
+            compiler: g++
+            build: embedded-static-libsystemd
+    steps:
+    - uses: actions/checkout@v2
+    - name: install-libsystemd-toolchain
+      if: matrix.build == 'embedded-static-libsystemd'
+      run: |
+        sudo apt-get update -y
+        sudo apt-get install -y meson ninja-build libcap-dev libmount-dev m4 gperf
+    - name: install-libsystemd-dev
+      if: matrix.build == 'shared-libsystemd'
+      run: |
+        sudo apt-get update -y
+        sudo apt-get install -y libsystemd-dev
+    - name: install-clang
+      if: matrix.compiler == 'clang'
+      run: |
+        sudo apt-get install -y clang
+        sudo update-alternatives --remove-all cc
+        sudo update-alternatives --install /usr/bin/cc cc /usr/bin/clang 10
+        sudo update-alternatives --remove-all c++
+        sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/clang++ 10
+    - name: configure-debug
+      if: matrix.build == 'shared-libsystemd' && matrix.os == 'ubuntu-18.04'
+      run: |
+        mkdir build
+        cd build
+        cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_FLAGS="-O0 -g -W -Wextra -Wall -Wnon-virtual-dtor -Werror" -DBUILD_TESTS=ON -DENABLE_PERF_TESTS=ON -DENABLE_STRESS_TESTS=ON -DBUILD_CODE_GEN=ON ..
+    - name: configure-release
+      if: matrix.build == 'shared-libsystemd' && matrix.os == 'ubuntu-20.04'
+      run: |
+        mkdir build
+        cd build
+        cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_FLAGS="-O3 -DNDEBUG -W -Wextra -Wall -Wnon-virtual-dtor -Werror" -DBUILD_TESTS=ON -DENABLE_PERF_TESTS=ON -DENABLE_STRESS_TESTS=ON -DBUILD_CODE_GEN=ON ..
+    - name: configure-with-embedded-libsystemd
+      if: matrix.build == 'embedded-static-libsystemd'
+      run: |
+        mkdir build
+        cd build
+        cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_TESTS=ON -DENABLE_PERF_TESTS=ON -DENABLE_STRESS_TESTS=ON -DBUILD_CODE_GEN=ON -DBUILD_LIBSYSTEMD=ON -DLIBSYSTEMD_VERSION=244 ..
+    - name: make
+      run: |
+        cd build
+        make -j2
+    - name: verify
+      run: |
+        cd build
+        sudo make install
+        ctest