ci: Intel icx/icpx via oneAPI

Add testing for Intel icx/icpx via the oneAPI images.
This is Intel's next-gen compiler and new C++ support, e.g. C++17 bug
fixes, first land here.

Update .github/workflows/ci.yml

Co-authored-by: Yannick Jadoul <yannick.jadoul@belgacom.net>

CMake: Fix ICPX Detection in Python tests

More IntelClang Detection

Upsi, keep ICC

rebased out by accident

Prettify

Compiler Workaround: Just in Configure

ci: rely on newer CMake

Author: ax3l

.github/workflows/ci.yml

@@ -566,6 +566,108 @@ jobs:
         cmake --build build-17 --target test_cmake_build
 
 
+  # Testing on ICX/ICPX, Intel's next-gen C/C++ compiler using the oneAPI apt repo
+  icx:
+    runs-on: ubuntu-20.04
+    strategy:
+      fail-fast: false
+
+    name: "🐍 3 • ICPX latest • x64"
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Add apt repo
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y wget build-essential pkg-config cmake ca-certificates gnupg
+        wget https://apt.repos.intel.com/intel-gpg-keys/GPG-PUB-KEY-INTEL-SW-PRODUCTS-2023.PUB
+        sudo apt-key add GPG-PUB-KEY-INTEL-SW-PRODUCTS-2023.PUB
+        echo "deb https://apt.repos.intel.com/oneapi all main" | sudo tee /etc/apt/sources.list.d/oneAPI.list
+
+    - name: Add ICPC & Python 3
+      run: sudo apt-get update; sudo apt-get install -y intel-oneapi-compiler-dpcpp-cpp cmake python3-dev python3-numpy python3-pytest python3-pip
+
+    - name: Update pip
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        python3 -m pip install --upgrade pip
+
+    - name: Install dependencies
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        python3 -m pip install -r tests/requirements.txt --prefer-binary
+
+    - name: Configure C++11
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        cmake -S . -B build-11          \
+        -DPYBIND11_WERROR=ON            \
+        -DDOWNLOAD_CATCH=ON             \
+        -DDOWNLOAD_EIGEN=OFF            \
+        -DCMAKE_CXX_STANDARD=14         \
+        -DCMAKE_VERBOSE_MAKEFILE=ON     \
+        -DCMAKE_CXX_COMPILER=$(which icpx)  \
+        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
+
+    - name: Build
+      shell: bash
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        cmake --build build-11 -j 2
+
+    - name: Python tests
+      shell: bash
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        sudo service apport stop
+        cmake --build build --target check
+
+    - name: C++ tests
+      shell: bash
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        cmake --build build --target cpptest
+
+    - name: Interface test
+      shell: bash
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        cmake --build build-11 --target test_cmake_build
+
+    - name: Configure C++17
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        cmake -S . -B build-17     \
+        -DPYBIND11_WERROR=ON    \
+        -DDOWNLOAD_CATCH=ON     \
+        -DDOWNLOAD_EIGEN=OFF    \
+        -DCMAKE_CXX_STANDARD=17             \
+        -DCMAKE_CXX_COMPILER=$(which icpx)  \
+        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
+
+    - name: Build C++17
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        cmake --build build-17 -j 2 -v
+
+    - name: Python tests C++17
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        sudo service apport stop
+        cmake --build build-17 --target check
+
+    - name: C++ tests C++17
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        cmake --build build-17 --target cpptest
+
+    - name: Interface test C++17
+      run: |
+        set +e; source /opt/intel/oneapi/setvars.sh; set -e
+        cmake --build build-17 --target test_cmake_build
+
+
   # Testing on CentOS (manylinux uses a centos base, and this is an easy way
   # to get GCC 4.8, which is the manylinux1 compiler).
   centos: