Set up CI builds for different gcc versions (commontk#80)

- uses GCC docker images to build with gcc 7, 9 and 11
- uses Python 3.7.3 / Qt 5.11.3 (gcc 7/9), Python 3.9.2 / Qt 5.15.2 (gcc 11)

.github/workflows/Dockerfile_gcc

@@ -0,0 +1,38 @@
+FROM gcc:#GCC#
+
+RUN apt-get update && apt-get install -y --force-yes \
+    unzip \
+    wget \
+    python3 \
+    python3-dev \
+    libpython3-dev \
+    qtbase5-dev \
+    qtbase5-private-dev \
+    qtchooser \
+    qt5-qmake \
+    qtbase5-dev-tools \
+    qttools5-dev \
+    qtdeclarative5-dev \
+    libqt5svg5* \
+    libqt5xmlpatterns5* \
+    libqt5multimedia5* \
+    libqt5multimediawidgets5* \
+    libqt5qml5* \
+    libqt5quickwidgets5* \
+    qtmultimedia5-dev
+RUN apt-get clean
+
+RUN mkdir -p work
+
+COPY . work/
+
+WORKDIR work
+
+ARG QT_SELECT=qt5
+RUN uname -a; gcc --version | grep "gcc"; python3 --version; qmake --version
+
+RUN qmake -r PythonQt.pro \
+    PYTHON_VERSION=$(python3 --version | cut -d " " -f 2 | cut -d "." -f1,2) \
+    PYTHON_DIR=$(which python3 | xargs dirname | xargs dirname)
+
+CMD ["make"]

.github/workflows/build.yml

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+name: Build
+
+on:
+  push:
+    branches: 
+      - master
+  pull_request:
+
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        runs-on: [ubuntu-latest]
+        gcc: [7, 9, 11]
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Setup docker container
+      shell: bash
+      run: |
+        cat $GITHUB_WORKSPACE/.github/workflows/Dockerfile_gcc | sed 's/#GCC#/${{ matrix.gcc }}/' > ./Dockerfile
+        docker build -t pythonqt -f ./Dockerfile . 
+    - name: Run docker
+      run: docker run -t pythonqt